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| author | Abseil Team <absl-team@google.com> | 2021-01-05 21:46:37 (GMT) |
|---|---|---|
| committer | Derek Mauro <dmauro@google.com> | 2021-01-14 01:59:12 (GMT) |
| commit | 489283524e3726b7adb9692763c2fb61b235d41a (patch) | |
| tree | 0c21fdc64b8978bcac9cee62f14584ce4f024bc9 /googlemock/docs | |
| parent | 996b65e64e415c683d7f15ee5926d66309425ce8 (diff) | |
| download | googletest-489283524e3726b7adb9692763c2fb61b235d41a.zip googletest-489283524e3726b7adb9692763c2fb61b235d41a.tar.gz googletest-489283524e3726b7adb9692763c2fb61b235d41a.tar.bz2 | |
Googletest export
Move all docs into top-level docs/ directory
PiperOrigin-RevId: 350211277
Diffstat (limited to 'googlemock/docs')
| -rw-r--r-- | googlemock/docs/README.md | 4 | ||||
| -rw-r--r-- | googlemock/docs/cheat_sheet.md | 786 | ||||
| -rw-r--r-- | googlemock/docs/community_created_documentation.md | 9 | ||||
| -rw-r--r-- | googlemock/docs/contribute.md | 5 | ||||
| -rw-r--r-- | googlemock/docs/cook_book.md | 4266 | ||||
| -rw-r--r-- | googlemock/docs/design.md | 1600 | ||||
| -rw-r--r-- | googlemock/docs/for_dummies.md | 702 | ||||
| -rw-r--r-- | googlemock/docs/gmock_faq.md | 398 | ||||
| -rw-r--r-- | googlemock/docs/guide.md | 49 | ||||
| -rw-r--r-- | googlemock/docs/index.md | 127 | ||||
| -rw-r--r-- | googlemock/docs/overview.md | 111 | ||||
| -rw-r--r-- | googlemock/docs/pump_manual.md | 189 | ||||
| -rw-r--r-- | googlemock/docs/sitemap.md | 11 | ||||
| -rw-r--r-- | googlemock/docs/under-construction-banner.md | 4 |
14 files changed, 4 insertions, 8257 deletions
diff --git a/googlemock/docs/README.md b/googlemock/docs/README.md new file mode 100644 index 0000000..1bc57b7 --- /dev/null +++ b/googlemock/docs/README.md @@ -0,0 +1,4 @@ +# Content Moved + +We are working on updates to the GoogleTest documentation, which has moved to +the top-level [docs](../../docs) directory. diff --git a/googlemock/docs/cheat_sheet.md b/googlemock/docs/cheat_sheet.md deleted file mode 100644 index dc2428e..0000000 --- a/googlemock/docs/cheat_sheet.md +++ /dev/null @@ -1,786 +0,0 @@ -# gMock Cheat Sheet - -<!-- GOOGLETEST_CM0019 DO NOT DELETE --> - -<!-- GOOGLETEST_CM0035 DO NOT DELETE --> - -<!-- GOOGLETEST_CM0033 DO NOT DELETE --> - -## Defining a Mock Class - -### Mocking a Normal Class {#MockClass} - -Given - -```cpp -class Foo { - ... - virtual ~Foo(); - virtual int GetSize() const = 0; - virtual string Describe(const char* name) = 0; - virtual string Describe(int type) = 0; - virtual bool Process(Bar elem, int count) = 0; -}; -``` - -(note that `~Foo()` **must** be virtual) we can define its mock as - -```cpp -#include "gmock/gmock.h" - -class MockFoo : public Foo { - ... - MOCK_METHOD(int, GetSize, (), (const, override)); - MOCK_METHOD(string, Describe, (const char* name), (override)); - MOCK_METHOD(string, Describe, (int type), (override)); - MOCK_METHOD(bool, Process, (Bar elem, int count), (override)); -}; -``` - -To create a "nice" mock, which ignores all uninteresting calls, a "naggy" mock, -which warns on all uninteresting calls, or a "strict" mock, which treats them as -failures: - -```cpp -using ::testing::NiceMock; -using ::testing::NaggyMock; -using ::testing::StrictMock; - -NiceMock<MockFoo> nice_foo; // The type is a subclass of MockFoo. -NaggyMock<MockFoo> naggy_foo; // The type is a subclass of MockFoo. -StrictMock<MockFoo> strict_foo; // The type is a subclass of MockFoo. -``` - -**Note:** A mock object is currently naggy by default. We may make it nice by -default in the future. - -### Mocking a Class Template {#MockTemplate} - -Class templates can be mocked just like any class. - -To mock - -```cpp -template <typename Elem> -class StackInterface { - ... - virtual ~StackInterface(); - virtual int GetSize() const = 0; - virtual void Push(const Elem& x) = 0; -}; -``` - -(note that all member functions that are mocked, including `~StackInterface()` -**must** be virtual). - -```cpp -template <typename Elem> -class MockStack : public StackInterface<Elem> { - ... - MOCK_METHOD(int, GetSize, (), (const, override)); - MOCK_METHOD(void, Push, (const Elem& x), (override)); -}; -``` - -### Specifying Calling Conventions for Mock Functions - -If your mock function doesn't use the default calling convention, you can -specify it by adding `Calltype(convention)` to `MOCK_METHOD`'s 4th parameter. -For example, - -```cpp - MOCK_METHOD(bool, Foo, (int n), (Calltype(STDMETHODCALLTYPE))); - MOCK_METHOD(int, Bar, (double x, double y), - (const, Calltype(STDMETHODCALLTYPE))); -``` - -where `STDMETHODCALLTYPE` is defined by `<objbase.h>` on Windows. - -## Using Mocks in Tests {#UsingMocks} - -The typical work flow is: - -1. Import the gMock names you need to use. All gMock symbols are in the - `testing` namespace unless they are macros or otherwise noted. -2. Create the mock objects. -3. Optionally, set the default actions of the mock objects. -4. Set your expectations on the mock objects (How will they be called? What - will they do?). -5. Exercise code that uses the mock objects; if necessary, check the result - using googletest assertions. -6. When a mock object is destructed, gMock automatically verifies that all - expectations on it have been satisfied. - -Here's an example: - -```cpp -using ::testing::Return; // #1 - -TEST(BarTest, DoesThis) { - MockFoo foo; // #2 - - ON_CALL(foo, GetSize()) // #3 - .WillByDefault(Return(1)); - // ... other default actions ... - - EXPECT_CALL(foo, Describe(5)) // #4 - .Times(3) - .WillRepeatedly(Return("Category 5")); - // ... other expectations ... - - EXPECT_EQ("good", MyProductionFunction(&foo)); // #5 -} // #6 -``` - -## Setting Default Actions {#OnCall} - -gMock has a **built-in default action** for any function that returns `void`, -`bool`, a numeric value, or a pointer. In C++11, it will additionally returns -the default-constructed value, if one exists for the given type. - -To customize the default action for functions with return type *`T`*: - -```cpp -using ::testing::DefaultValue; - -// Sets the default value to be returned. T must be CopyConstructible. -DefaultValue<T>::Set(value); -// Sets a factory. Will be invoked on demand. T must be MoveConstructible. -// T MakeT(); -DefaultValue<T>::SetFactory(&MakeT); -// ... use the mocks ... -// Resets the default value. -DefaultValue<T>::Clear(); -``` - -Example usage: - -```cpp - // Sets the default action for return type std::unique_ptr<Buzz> to - // creating a new Buzz every time. - DefaultValue<std::unique_ptr<Buzz>>::SetFactory( - [] { return MakeUnique<Buzz>(AccessLevel::kInternal); }); - - // When this fires, the default action of MakeBuzz() will run, which - // will return a new Buzz object. - EXPECT_CALL(mock_buzzer_, MakeBuzz("hello")).Times(AnyNumber()); - - auto buzz1 = mock_buzzer_.MakeBuzz("hello"); - auto buzz2 = mock_buzzer_.MakeBuzz("hello"); - EXPECT_NE(nullptr, buzz1); - EXPECT_NE(nullptr, buzz2); - EXPECT_NE(buzz1, buzz2); - - // Resets the default action for return type std::unique_ptr<Buzz>, - // to avoid interfere with other tests. - DefaultValue<std::unique_ptr<Buzz>>::Clear(); -``` - -To customize the default action for a particular method of a specific mock -object, use `ON_CALL()`. `ON_CALL()` has a similar syntax to `EXPECT_CALL()`, -but it is used for setting default behaviors (when you do not require that the -mock method is called). See [here](cook_book.md#UseOnCall) for a more detailed -discussion. - -```cpp -ON_CALL(mock-object, method(matchers)) - .With(multi-argument-matcher) ? - .WillByDefault(action); -``` - -## Setting Expectations {#ExpectCall} - -`EXPECT_CALL()` sets **expectations** on a mock method (How will it be called? -What will it do?): - -```cpp -EXPECT_CALL(mock-object, method (matchers)?) - .With(multi-argument-matcher) ? - .Times(cardinality) ? - .InSequence(sequences) * - .After(expectations) * - .WillOnce(action) * - .WillRepeatedly(action) ? - .RetiresOnSaturation(); ? -``` - -For each item above, `?` means it can be used at most once, while `*` means it -can be used any number of times. - -In order to pass, `EXPECT_CALL` must be used before the calls are actually made. - -The `(matchers)` is a comma-separated list of matchers that correspond to each -of the arguments of `method`, and sets the expectation only for calls of -`method` that matches all of the matchers. - -If `(matchers)` is omitted, the expectation is the same as if the matchers were -set to anything matchers (for example, `(_, _, _, _)` for a four-arg method). - -If `Times()` is omitted, the cardinality is assumed to be: - -* `Times(1)` when there is neither `WillOnce()` nor `WillRepeatedly()`; -* `Times(n)` when there are `n` `WillOnce()`s but no `WillRepeatedly()`, where - `n` >= 1; or -* `Times(AtLeast(n))` when there are `n` `WillOnce()`s and a - `WillRepeatedly()`, where `n` >= 0. - -A method with no `EXPECT_CALL()` is free to be invoked *any number of times*, -and the default action will be taken each time. - -## Matchers {#MatcherList} - -<!-- GOOGLETEST_CM0020 DO NOT DELETE --> - -A **matcher** matches a *single* argument. You can use it inside `ON_CALL()` or -`EXPECT_CALL()`, or use it to validate a value directly using two macros: - -<!-- mdformat off(github rendering does not support multiline tables) --> -| Macro | Description | -| :----------------------------------- | :------------------------------------ | -| `EXPECT_THAT(actual_value, matcher)` | Asserts that `actual_value` matches `matcher`. | -| `ASSERT_THAT(actual_value, matcher)` | The same as `EXPECT_THAT(actual_value, matcher)`, except that it generates a **fatal** failure. | -<!-- mdformat on --> - -**Note:** Although equality matching via `EXPECT_THAT(actual_value, -expected_value)` is supported, prefer to make the comparison explicit via -`EXPECT_THAT(actual_value, Eq(expected_value))` or `EXPECT_EQ(actual_value, -expected_value)`. - -Built-in matchers (where `argument` is the function argument, e.g. -`actual_value` in the example above, or when used in the context of -`EXPECT_CALL(mock_object, method(matchers))`, the arguments of `method`) are -divided into several categories: - -### Wildcard - -Matcher | Description -:-------------------------- | :----------------------------------------------- -`_` | `argument` can be any value of the correct type. -`A<type>()` or `An<type>()` | `argument` can be any value of type `type`. - -### Generic Comparison - -<!-- mdformat off(no multiline tables) --> -| Matcher | Description | -| :--------------------- | :-------------------------------------------------- | -| `Eq(value)` or `value` | `argument == value` | -| `Ge(value)` | `argument >= value` | -| `Gt(value)` | `argument > value` | -| `Le(value)` | `argument <= value` | -| `Lt(value)` | `argument < value` | -| `Ne(value)` | `argument != value` | -| `IsFalse()` | `argument` evaluates to `false` in a Boolean context. | -| `IsTrue()` | `argument` evaluates to `true` in a Boolean context. | -| `IsNull()` | `argument` is a `NULL` pointer (raw or smart). | -| `NotNull()` | `argument` is a non-null pointer (raw or smart). | -| `Optional(m)` | `argument` is `optional<>` that contains a value matching `m`. (For testing whether an `optional<>` is set, check for equality with `nullopt`. You may need to use `Eq(nullopt)` if the inner type doesn't have `==`.)| -| `VariantWith<T>(m)` | `argument` is `variant<>` that holds the alternative of type T with a value matching `m`. | -| `Ref(variable)` | `argument` is a reference to `variable`. | -| `TypedEq<type>(value)` | `argument` has type `type` and is equal to `value`. You may need to use this instead of `Eq(value)` when the mock function is overloaded. | -<!-- mdformat on --> - -Except `Ref()`, these matchers make a *copy* of `value` in case it's modified or -destructed later. If the compiler complains that `value` doesn't have a public -copy constructor, try wrap it in `std::ref()`, e.g. -`Eq(std::ref(non_copyable_value))`. If you do that, make sure -`non_copyable_value` is not changed afterwards, or the meaning of your matcher -will be changed. - -`IsTrue` and `IsFalse` are useful when you need to use a matcher, or for types -that can be explicitly converted to Boolean, but are not implicitly converted to -Boolean. In other cases, you can use the basic -[`EXPECT_TRUE` and `EXPECT_FALSE`](../../googletest/docs/primer#basic-assertions) -assertions. - -### Floating-Point Matchers {#FpMatchers} - -<!-- mdformat off(no multiline tables) --> -| Matcher | Description | -| :------------------------------- | :--------------------------------- | -| `DoubleEq(a_double)` | `argument` is a `double` value approximately equal to `a_double`, treating two NaNs as unequal. | -| `FloatEq(a_float)` | `argument` is a `float` value approximately equal to `a_float`, treating two NaNs as unequal. | -| `NanSensitiveDoubleEq(a_double)` | `argument` is a `double` value approximately equal to `a_double`, treating two NaNs as equal. | -| `NanSensitiveFloatEq(a_float)` | `argument` is a `float` value approximately equal to `a_float`, treating two NaNs as equal. | -| `IsNan()` | `argument` is any floating-point type with a NaN value. | -<!-- mdformat on --> - -The above matchers use ULP-based comparison (the same as used in googletest). -They automatically pick a reasonable error bound based on the absolute value of -the expected value. `DoubleEq()` and `FloatEq()` conform to the IEEE standard, -which requires comparing two NaNs for equality to return false. The -`NanSensitive*` version instead treats two NaNs as equal, which is often what a -user wants. - -<!-- mdformat off(no multiline tables) --> -| Matcher | Description | -| :------------------------------------------------ | :----------------------- | -| `DoubleNear(a_double, max_abs_error)` | `argument` is a `double` value close to `a_double` (absolute error <= `max_abs_error`), treating two NaNs as unequal. | -| `FloatNear(a_float, max_abs_error)` | `argument` is a `float` value close to `a_float` (absolute error <= `max_abs_error`), treating two NaNs as unequal. | -| `NanSensitiveDoubleNear(a_double, max_abs_error)` | `argument` is a `double` value close to `a_double` (absolute error <= `max_abs_error`), treating two NaNs as equal. | -| `NanSensitiveFloatNear(a_float, max_abs_error)` | `argument` is a `float` value close to `a_float` (absolute error <= `max_abs_error`), treating two NaNs as equal. | -<!-- mdformat on --> - -### String Matchers - -The `argument` can be either a C string or a C++ string object: - -<!-- mdformat off(no multiline tables) --> -| Matcher | Description | -| :---------------------- | :------------------------------------------------- | -| `ContainsRegex(string)` | `argument` matches the given regular expression. | -| `EndsWith(suffix)` | `argument` ends with string `suffix`. | -| `HasSubstr(string)` | `argument` contains `string` as a sub-string. | -| `MatchesRegex(string)` | `argument` matches the given regular expression with the match starting at the first character and ending at the last character. | -| `StartsWith(prefix)` | `argument` starts with string `prefix`. | -| `StrCaseEq(string)` | `argument` is equal to `string`, ignoring case. | -| `StrCaseNe(string)` | `argument` is not equal to `string`, ignoring case. | -| `StrEq(string)` | `argument` is equal to `string`. | -| `StrNe(string)` | `argument` is not equal to `string`. | -<!-- mdformat on --> - -`ContainsRegex()` and `MatchesRegex()` take ownership of the `RE` object. They -use the regular expression syntax defined -[here](../../googletest/docs/advanced.md#regular-expression-syntax). All of -these matchers, except `ContainsRegex()` and `MatchesRegex()` work for wide -strings as well. - -### Container Matchers - -Most STL-style containers support `==`, so you can use `Eq(expected_container)` -or simply `expected_container` to match a container exactly. If you want to -write the elements in-line, match them more flexibly, or get more informative -messages, you can use: - -<!-- mdformat off(no multiline tables) --> -| Matcher | Description | -| :---------------------------------------- | :------------------------------- | -| `BeginEndDistanceIs(m)` | `argument` is a container whose `begin()` and `end()` iterators are separated by a number of increments matching `m`. E.g. `BeginEndDistanceIs(2)` or `BeginEndDistanceIs(Lt(2))`. For containers that define a `size()` method, `SizeIs(m)` may be more efficient. | -| `ContainerEq(container)` | The same as `Eq(container)` except that the failure message also includes which elements are in one container but not the other. | -| `Contains(e)` | `argument` contains an element that matches `e`, which can be either a value or a matcher. | -| `Each(e)` | `argument` is a container where *every* element matches `e`, which can be either a value or a matcher. | -| `ElementsAre(e0, e1, ..., en)` | `argument` has `n + 1` elements, where the *i*-th element matches `ei`, which can be a value or a matcher. | -| `ElementsAreArray({e0, e1, ..., en})`, `ElementsAreArray(a_container)`, `ElementsAreArray(begin, end)`, `ElementsAreArray(array)`, or `ElementsAreArray(array, count)` | The same as `ElementsAre()` except that the expected element values/matchers come from an initializer list, STL-style container, iterator range, or C-style array. | -| `IsEmpty()` | `argument` is an empty container (`container.empty()`). | -| `IsSubsetOf({e0, e1, ..., en})`, `IsSubsetOf(a_container)`, `IsSubsetOf(begin, end)`, `IsSubsetOf(array)`, or `IsSubsetOf(array, count)` | `argument` matches `UnorderedElementsAre(x0, x1, ..., xk)` for some subset `{x0, x1, ..., xk}` of the expected matchers. | -| `IsSupersetOf({e0, e1, ..., en})`, `IsSupersetOf(a_container)`, `IsSupersetOf(begin, end)`, `IsSupersetOf(array)`, or `IsSupersetOf(array, count)` | Some subset of `argument` matches `UnorderedElementsAre(`expected matchers`)`. | -| `Pointwise(m, container)`, `Pointwise(m, {e0, e1, ..., en})` | `argument` contains the same number of elements as in `container`, and for all i, (the i-th element in `argument`, the i-th element in `container`) match `m`, which is a matcher on 2-tuples. E.g. `Pointwise(Le(), upper_bounds)` verifies that each element in `argument` doesn't exceed the corresponding element in `upper_bounds`. See more detail below. | -| `SizeIs(m)` | `argument` is a container whose size matches `m`. E.g. `SizeIs(2)` or `SizeIs(Lt(2))`. | -| `UnorderedElementsAre(e0, e1, ..., en)` | `argument` has `n + 1` elements, and under *some* permutation of the elements, each element matches an `ei` (for a different `i`), which can be a value or a matcher. | -| `UnorderedElementsAreArray({e0, e1, ..., en})`, `UnorderedElementsAreArray(a_container)`, `UnorderedElementsAreArray(begin, end)`, `UnorderedElementsAreArray(array)`, or `UnorderedElementsAreArray(array, count)` | The same as `UnorderedElementsAre()` except that the expected element values/matchers come from an initializer list, STL-style container, iterator range, or C-style array. | -| `UnorderedPointwise(m, container)`, `UnorderedPointwise(m, {e0, e1, ..., en})` | Like `Pointwise(m, container)`, but ignores the order of elements. | -| `WhenSorted(m)` | When `argument` is sorted using the `<` operator, it matches container matcher `m`. E.g. `WhenSorted(ElementsAre(1, 2, 3))` verifies that `argument` contains elements 1, 2, and 3, ignoring order. | -| `WhenSortedBy(comparator, m)` | The same as `WhenSorted(m)`, except that the given comparator instead of `<` is used to sort `argument`. E.g. `WhenSortedBy(std::greater(), ElementsAre(3, 2, 1))`. | -<!-- mdformat on --> - -**Notes:** - -* These matchers can also match: - 1. a native array passed by reference (e.g. in `Foo(const int (&a)[5])`), - and - 2. an array passed as a pointer and a count (e.g. in `Bar(const T* buffer, - int len)` -- see [Multi-argument Matchers](#MultiArgMatchers)). -* The array being matched may be multi-dimensional (i.e. its elements can be - arrays). -* `m` in `Pointwise(m, ...)` should be a matcher for `::std::tuple<T, U>` - where `T` and `U` are the element type of the actual container and the - expected container, respectively. For example, to compare two `Foo` - containers where `Foo` doesn't support `operator==`, one might write: - - ```cpp - using ::std::get; - MATCHER(FooEq, "") { - return std::get<0>(arg).Equals(std::get<1>(arg)); - } - ... - EXPECT_THAT(actual_foos, Pointwise(FooEq(), expected_foos)); - ``` - -### Member Matchers - -<!-- mdformat off(no multiline tables) --> -| Matcher | Description | -| :------------------------------ | :----------------------------------------- | -| `Field(&class::field, m)` | `argument.field` (or `argument->field` when `argument` is a plain pointer) matches matcher `m`, where `argument` is an object of type _class_. | -| `Key(e)` | `argument.first` matches `e`, which can be either a value or a matcher. E.g. `Contains(Key(Le(5)))` can verify that a `map` contains a key `<= 5`. | -| `Pair(m1, m2)` | `argument` is an `std::pair` whose `first` field matches `m1` and `second` field matches `m2`. | -| `FieldsAre(m...)` | `argument` is a compatible object where each field matches piecewise with `m...`. A compatible object is any that supports the `std::tuple_size<Obj>`+`get<I>(obj)` protocol. In C++17 and up this also supports types compatible with structured bindings, like aggregates. | -| `Property(&class::property, m)` | `argument.property()` (or `argument->property()` when `argument` is a plain pointer) matches matcher `m`, where `argument` is an object of type _class_. | -<!-- mdformat on --> - -### Matching the Result of a Function, Functor, or Callback - -<!-- mdformat off(no multiline tables) --> -| Matcher | Description | -| :--------------- | :------------------------------------------------ | -| `ResultOf(f, m)` | `f(argument)` matches matcher `m`, where `f` is a function or functor. | -<!-- mdformat on --> - -### Pointer Matchers - -<!-- mdformat off(no multiline tables) --> -| Matcher | Description | -| :------------------------ | :---------------------------------------------- | -| `Address(m)` | the result of `std::addressof(argument)` matches `m`. | -| `Pointee(m)` | `argument` (either a smart pointer or a raw pointer) points to a value that matches matcher `m`. | -| `Pointer(m)` | `argument` (either a smart pointer or a raw pointer) contains a pointer that matches `m`. `m` will match against the raw pointer regardless of the type of `argument`. | -| `WhenDynamicCastTo<T>(m)` | when `argument` is passed through `dynamic_cast<T>()`, it matches matcher `m`. | -<!-- mdformat on --> - -<!-- GOOGLETEST_CM0026 DO NOT DELETE --> - -<!-- GOOGLETEST_CM0027 DO NOT DELETE --> - -### Multi-argument Matchers {#MultiArgMatchers} - -Technically, all matchers match a *single* value. A "multi-argument" matcher is -just one that matches a *tuple*. The following matchers can be used to match a -tuple `(x, y)`: - -Matcher | Description -:------ | :---------- -`Eq()` | `x == y` -`Ge()` | `x >= y` -`Gt()` | `x > y` -`Le()` | `x <= y` -`Lt()` | `x < y` -`Ne()` | `x != y` - -You can use the following selectors to pick a subset of the arguments (or -reorder them) to participate in the matching: - -<!-- mdformat off(no multiline tables) --> -| Matcher | Description | -| :------------------------- | :---------------------------------------------- | -| `AllArgs(m)` | Equivalent to `m`. Useful as syntactic sugar in `.With(AllArgs(m))`. | -| `Args<N1, N2, ..., Nk>(m)` | The tuple of the `k` selected (using 0-based indices) arguments matches `m`, e.g. `Args<1, 2>(Eq())`. | -<!-- mdformat on --> - -### Composite Matchers - -You can make a matcher from one or more other matchers: - -<!-- mdformat off(no multiline tables) --> -| Matcher | Description | -| :------------------------------- | :-------------------------------------- | -| `AllOf(m1, m2, ..., mn)` | `argument` matches all of the matchers `m1` to `mn`. | -| `AllOfArray({m0, m1, ..., mn})`, `AllOfArray(a_container)`, `AllOfArray(begin, end)`, `AllOfArray(array)`, or `AllOfArray(array, count)` | The same as `AllOf()` except that the matchers come from an initializer list, STL-style container, iterator range, or C-style array. | -| `AnyOf(m1, m2, ..., mn)` | `argument` matches at least one of the matchers `m1` to `mn`. | -| `AnyOfArray({m0, m1, ..., mn})`, `AnyOfArray(a_container)`, `AnyOfArray(begin, end)`, `AnyOfArray(array)`, or `AnyOfArray(array, count)` | The same as `AnyOf()` except that the matchers come from an initializer list, STL-style container, iterator range, or C-style array. | -| `Not(m)` | `argument` doesn't match matcher `m`. | -<!-- mdformat on --> - -<!-- GOOGLETEST_CM0028 DO NOT DELETE --> - -### Adapters for Matchers - -<!-- mdformat off(no multiline tables) --> -| Matcher | Description | -| :---------------------- | :------------------------------------ | -| `MatcherCast<T>(m)` | casts matcher `m` to type `Matcher<T>`. | -| `SafeMatcherCast<T>(m)` | [safely casts](cook_book.md#casting-matchers) matcher `m` to type `Matcher<T>`. | -| `Truly(predicate)` | `predicate(argument)` returns something considered by C++ to be true, where `predicate` is a function or functor. | -<!-- mdformat on --> - -`AddressSatisfies(callback)` and `Truly(callback)` take ownership of `callback`, -which must be a permanent callback. - -### Using Matchers as Predicates {#MatchersAsPredicatesCheat} - -<!-- mdformat off(no multiline tables) --> -| Matcher | Description | -| :---------------------------- | :------------------------------------------ | -| `Matches(m)(value)` | evaluates to `true` if `value` matches `m`. You can use `Matches(m)` alone as a unary functor. | -| `ExplainMatchResult(m, value, result_listener)` | evaluates to `true` if `value` matches `m`, explaining the result to `result_listener`. | -| `Value(value, m)` | evaluates to `true` if `value` matches `m`. | -<!-- mdformat on --> - -### Defining Matchers - -<!-- mdformat off(no multiline tables) --> -| Matcher | Description | -| :----------------------------------- | :------------------------------------ | -| `MATCHER(IsEven, "") { return (arg % 2) == 0; }` | Defines a matcher `IsEven()` to match an even number. | -| `MATCHER_P(IsDivisibleBy, n, "") { *result_listener << "where the remainder is " << (arg % n); return (arg % n) == 0; }` | Defines a matcher `IsDivisibleBy(n)` to match a number divisible by `n`. | -| `MATCHER_P2(IsBetween, a, b, absl::StrCat(negation ? "isn't" : "is", " between ", PrintToString(a), " and ", PrintToString(b))) { return a <= arg && arg <= b; }` | Defines a matcher `IsBetween(a, b)` to match a value in the range [`a`, `b`]. | -<!-- mdformat on --> - -**Notes:** - -1. The `MATCHER*` macros cannot be used inside a function or class. -2. The matcher body must be *purely functional* (i.e. it cannot have any side - effect, and the result must not depend on anything other than the value - being matched and the matcher parameters). -3. You can use `PrintToString(x)` to convert a value `x` of any type to a - string. - -## Actions {#ActionList} - -**Actions** specify what a mock function should do when invoked. - -### Returning a Value - -<!-- mdformat off(no multiline tables) --> -| | | -| :-------------------------------- | :-------------------------------------------- | -| `Return()` | Return from a `void` mock function. | -| `Return(value)` | Return `value`. If the type of `value` is different to the mock function's return type, `value` is converted to the latter type <i>at the time the expectation is set</i>, not when the action is executed. | -| `ReturnArg<N>()` | Return the `N`-th (0-based) argument. | -| `ReturnNew<T>(a1, ..., ak)` | Return `new T(a1, ..., ak)`; a different object is created each time. | -| `ReturnNull()` | Return a null pointer. | -| `ReturnPointee(ptr)` | Return the value pointed to by `ptr`. | -| `ReturnRef(variable)` | Return a reference to `variable`. | -| `ReturnRefOfCopy(value)` | Return a reference to a copy of `value`; the copy lives as long as the action. | -| `ReturnRoundRobin({a1, ..., ak})` | Each call will return the next `ai` in the list, starting at the beginning when the end of the list is reached. | -<!-- mdformat on --> - -### Side Effects - -<!-- mdformat off(no multiline tables) --> -| | | -| :--------------------------------- | :-------------------------------------- | -| `Assign(&variable, value)` | Assign `value` to variable. | -| `DeleteArg<N>()` | Delete the `N`-th (0-based) argument, which must be a pointer. | -| `SaveArg<N>(pointer)` | Save the `N`-th (0-based) argument to `*pointer`. | -| `SaveArgPointee<N>(pointer)` | Save the value pointed to by the `N`-th (0-based) argument to `*pointer`. | -| `SetArgReferee<N>(value)` | Assign `value` to the variable referenced by the `N`-th (0-based) argument. | -| `SetArgPointee<N>(value)` | Assign `value` to the variable pointed by the `N`-th (0-based) argument. | -| `SetArgumentPointee<N>(value)` | Same as `SetArgPointee<N>(value)`. Deprecated. Will be removed in v1.7.0. | -| `SetArrayArgument<N>(first, last)` | Copies the elements in source range [`first`, `last`) to the array pointed to by the `N`-th (0-based) argument, which can be either a pointer or an iterator. The action does not take ownership of the elements in the source range. | -| `SetErrnoAndReturn(error, value)` | Set `errno` to `error` and return `value`. | -| `Throw(exception)` | Throws the given exception, which can be any copyable value. Available since v1.1.0. | -<!-- mdformat on --> - -### Using a Function, Functor, or Lambda as an Action - -In the following, by "callable" we mean a free function, `std::function`, -functor, or lambda. - -<!-- mdformat off(no multiline tables) --> -| | | -| :---------------------------------- | :------------------------------------- | -| `f` | Invoke f with the arguments passed to the mock function, where f is a callable. | -| `Invoke(f)` | Invoke `f` with the arguments passed to the mock function, where `f` can be a global/static function or a functor. | -| `Invoke(object_pointer, &class::method)` | Invoke the method on the object with the arguments passed to the mock function. | -| `InvokeWithoutArgs(f)` | Invoke `f`, which can be a global/static function or a functor. `f` must take no arguments. | -| `InvokeWithoutArgs(object_pointer, &class::method)` | Invoke the method on the object, which takes no arguments. | -| `InvokeArgument<N>(arg1, arg2, ..., argk)` | Invoke the mock function's `N`-th (0-based) argument, which must be a function or a functor, with the `k` arguments. | -<!-- mdformat on --> - -The return value of the invoked function is used as the return value of the -action. - -When defining a callable to be used with `Invoke*()`, you can declare any unused -parameters as `Unused`: - -```cpp -using ::testing::Invoke; -double Distance(Unused, double x, double y) { return sqrt(x*x + y*y); } -... -EXPECT_CALL(mock, Foo("Hi", _, _)).WillOnce(Invoke(Distance)); -``` - -`Invoke(callback)` and `InvokeWithoutArgs(callback)` take ownership of -`callback`, which must be permanent. The type of `callback` must be a base -callback type instead of a derived one, e.g. - -```cpp - BlockingClosure* done = new BlockingClosure; - ... Invoke(done) ...; // This won't compile! - - Closure* done2 = new BlockingClosure; - ... Invoke(done2) ...; // This works. -``` - -In `InvokeArgument<N>(...)`, if an argument needs to be passed by reference, -wrap it inside `std::ref()`. For example, - -```cpp -using ::testing::InvokeArgument; -... -InvokeArgument<2>(5, string("Hi"), std::ref(foo)) -``` - -calls the mock function's #2 argument, passing to it `5` and `string("Hi")` by -value, and `foo` by reference. - -### Default Action - -<!-- mdformat off(no multiline tables) --> -| Matcher | Description | -| :------------ | :----------------------------------------------------- | -| `DoDefault()` | Do the default action (specified by `ON_CALL()` or the built-in one). | -<!-- mdformat on --> - -**Note:** due to technical reasons, `DoDefault()` cannot be used inside a -composite action - trying to do so will result in a run-time error. - -<!-- GOOGLETEST_CM0032 DO NOT DELETE --> - -### Composite Actions - -<!-- mdformat off(no multiline tables) --> -| | | -| :----------------------------- | :------------------------------------------ | -| `DoAll(a1, a2, ..., an)` | Do all actions `a1` to `an` and return the result of `an` in each invocation. The first `n - 1` sub-actions must return void and will receive a readonly view of the arguments. | -| `IgnoreResult(a)` | Perform action `a` and ignore its result. `a` must not return void. | -| `WithArg<N>(a)` | Pass the `N`-th (0-based) argument of the mock function to action `a` and perform it. | -| `WithArgs<N1, N2, ..., Nk>(a)` | Pass the selected (0-based) arguments of the mock function to action `a` and perform it. | -| `WithoutArgs(a)` | Perform action `a` without any arguments. | -<!-- mdformat on --> - -### Defining Actions - -<!-- mdformat off(no multiline tables) --> -| | | -| :--------------------------------- | :-------------------------------------- | -| `ACTION(Sum) { return arg0 + arg1; }` | Defines an action `Sum()` to return the sum of the mock function's argument #0 and #1. | -| `ACTION_P(Plus, n) { return arg0 + n; }` | Defines an action `Plus(n)` to return the sum of the mock function's argument #0 and `n`. | -| `ACTION_Pk(Foo, p1, ..., pk) { statements; }` | Defines a parameterized action `Foo(p1, ..., pk)` to execute the given `statements`. | -<!-- mdformat on --> - -The `ACTION*` macros cannot be used inside a function or class. - -## Cardinalities {#CardinalityList} - -These are used in `Times()` to specify how many times a mock function will be -called: - -<!-- mdformat off(no multiline tables) --> -| | | -| :---------------- | :----------------------------------------------------- | -| `AnyNumber()` | The function can be called any number of times. | -| `AtLeast(n)` | The call is expected at least `n` times. | -| `AtMost(n)` | The call is expected at most `n` times. | -| `Between(m, n)` | The call is expected between `m` and `n` (inclusive) times. | -| `Exactly(n) or n` | The call is expected exactly `n` times. In particular, the call should never happen when `n` is 0. | -<!-- mdformat on --> - -## Expectation Order - -By default, the expectations can be matched in *any* order. If some or all -expectations must be matched in a given order, there are two ways to specify it. -They can be used either independently or together. - -### The After Clause {#AfterClause} - -```cpp -using ::testing::Expectation; -... -Expectation init_x = EXPECT_CALL(foo, InitX()); -Expectation init_y = EXPECT_CALL(foo, InitY()); -EXPECT_CALL(foo, Bar()) - .After(init_x, init_y); -``` - -says that `Bar()` can be called only after both `InitX()` and `InitY()` have -been called. - -If you don't know how many pre-requisites an expectation has when you write it, -you can use an `ExpectationSet` to collect them: - -```cpp -using ::testing::ExpectationSet; -... -ExpectationSet all_inits; -for (int i = 0; i < element_count; i++) { - all_inits += EXPECT_CALL(foo, InitElement(i)); -} -EXPECT_CALL(foo, Bar()) - .After(all_inits); -``` - -says that `Bar()` can be called only after all elements have been initialized -(but we don't care about which elements get initialized before the others). - -Modifying an `ExpectationSet` after using it in an `.After()` doesn't affect the -meaning of the `.After()`. - -### Sequences {#UsingSequences} - -When you have a long chain of sequential expectations, it's easier to specify -the order using **sequences**, which don't require you to given each expectation -in the chain a different name. *All expected calls* in the same sequence must -occur in the order they are specified. - -```cpp -using ::testing::Return; -using ::testing::Sequence; -Sequence s1, s2; -... -EXPECT_CALL(foo, Reset()) - .InSequence(s1, s2) - .WillOnce(Return(true)); -EXPECT_CALL(foo, GetSize()) - .InSequence(s1) - .WillOnce(Return(1)); -EXPECT_CALL(foo, Describe(A<const char*>())) - .InSequence(s2) - .WillOnce(Return("dummy")); -``` - -says that `Reset()` must be called before *both* `GetSize()` *and* `Describe()`, -and the latter two can occur in any order. - -To put many expectations in a sequence conveniently: - -```cpp -using ::testing::InSequence; -{ - InSequence seq; - - EXPECT_CALL(...)...; - EXPECT_CALL(...)...; - ... - EXPECT_CALL(...)...; -} -``` - -says that all expected calls in the scope of `seq` must occur in strict order. -The name `seq` is irrelevant. - -## Verifying and Resetting a Mock - -gMock will verify the expectations on a mock object when it is destructed, or -you can do it earlier: - -```cpp -using ::testing::Mock; -... -// Verifies and removes the expectations on mock_obj; -// returns true if and only if successful. -Mock::VerifyAndClearExpectations(&mock_obj); -... -// Verifies and removes the expectations on mock_obj; -// also removes the default actions set by ON_CALL(); -// returns true if and only if successful. -Mock::VerifyAndClear(&mock_obj); -``` - -You can also tell gMock that a mock object can be leaked and doesn't need to be -verified: - -```cpp -Mock::AllowLeak(&mock_obj); -``` - -## Mock Classes - -gMock defines a convenient mock class template - -```cpp -class MockFunction<R(A1, ..., An)> { - public: - MOCK_METHOD(R, Call, (A1, ..., An)); -}; -``` - -See this [recipe](cook_book.md#using-check-points) for one application of it. - -## Flags - -<!-- mdformat off(no multiline tables) --> -| Flag | Description | -| :----------------------------- | :---------------------------------------- | -| `--gmock_catch_leaked_mocks=0` | Don't report leaked mock objects as failures. | -| `--gmock_verbose=LEVEL` | Sets the default verbosity level (`info`, `warning`, or `error`) of Google Mock messages. | -<!-- mdformat on --> diff --git a/googlemock/docs/community_created_documentation.md b/googlemock/docs/community_created_documentation.md deleted file mode 100644 index dfd87f7..0000000 --- a/googlemock/docs/community_created_documentation.md +++ /dev/null @@ -1,9 +0,0 @@ -# Community-Created Documentation - -go/gunit-community-created-docs - -The following is a list, in no particular order, of links to documentation -created by the Googletest community. - -* [Googlemock Insights](https://github.com/ElectricRCAircraftGuy/eRCaGuy_dotfiles/blob/master/googletest/insights.md), - by [ElectricRCAircraftGuy](https://github.com/ElectricRCAircraftGuy) diff --git a/googlemock/docs/contribute.md b/googlemock/docs/contribute.md deleted file mode 100644 index 087654c..0000000 --- a/googlemock/docs/contribute.md +++ /dev/null @@ -1,5 +0,0 @@ -# How to Contribute - -googletest development is Piper-First. Just create a regular Piper CL. When the -CL is accepted and submitted, it will make its way to OSS via regular releasing -process. diff --git a/googlemock/docs/cook_book.md b/googlemock/docs/cook_book.md deleted file mode 100644 index cd64150..0000000 --- a/googlemock/docs/cook_book.md +++ /dev/null @@ -1,4266 +0,0 @@ -# gMock Cookbook - -<!-- GOOGLETEST_CM0012 DO NOT DELETE --> - -You can find recipes for using gMock here. If you haven't yet, please read -[the dummy guide](for_dummies.md) first to make sure you understand the basics. - -**Note:** gMock lives in the `testing` name space. For readability, it is -recommended to write `using ::testing::Foo;` once in your file before using the -name `Foo` defined by gMock. We omit such `using` statements in this section for -brevity, but you should do it in your own code. - -<!-- GOOGLETEST_CM0035 DO NOT DELETE --> - -## Creating Mock Classes - -Mock classes are defined as normal classes, using the `MOCK_METHOD` macro to -generate mocked methods. The macro gets 3 or 4 parameters: - -```cpp -class MyMock { - public: - MOCK_METHOD(ReturnType, MethodName, (Args...)); - MOCK_METHOD(ReturnType, MethodName, (Args...), (Specs...)); -}; -``` - -The first 3 parameters are simply the method declaration, split into 3 parts. -The 4th parameter accepts a closed list of qualifiers, which affect the -generated method: - -* **`const`** - Makes the mocked method a `const` method. Required if - overriding a `const` method. -* **`override`** - Marks the method with `override`. Recommended if overriding - a `virtual` method. -* **`noexcept`** - Marks the method with `noexcept`. Required if overriding a - `noexcept` method. -* **`Calltype(...)`** - Sets the call type for the method (e.g. to - `STDMETHODCALLTYPE`), useful in Windows. -* **`ref(...)`** - Marks the method with the reference qualification - specified. Required if overriding a method that has reference - qualifications. Eg `ref(&)` or `ref(&&)`. - -### Dealing with unprotected commas - -Unprotected commas, i.e. commas which are not surrounded by parentheses, prevent -`MOCK_METHOD` from parsing its arguments correctly: - -```cpp {.bad} -class MockFoo { - public: - MOCK_METHOD(std::pair<bool, int>, GetPair, ()); // Won't compile! - MOCK_METHOD(bool, CheckMap, (std::map<int, double>, bool)); // Won't compile! -}; -``` - -Solution 1 - wrap with parentheses: - -```cpp {.good} -class MockFoo { - public: - MOCK_METHOD((std::pair<bool, int>), GetPair, ()); - MOCK_METHOD(bool, CheckMap, ((std::map<int, double>), bool)); -}; -``` - -Note that wrapping a return or argument type with parentheses is, in general, -invalid C++. `MOCK_METHOD` removes the parentheses. - -Solution 2 - define an alias: - -```cpp {.good} -class MockFoo { - public: - using BoolAndInt = std::pair<bool, int>; - MOCK_METHOD(BoolAndInt, GetPair, ()); - using MapIntDouble = std::map<int, double>; - MOCK_METHOD(bool, CheckMap, (MapIntDouble, bool)); -}; -``` - -### Mocking Private or Protected Methods - -You must always put a mock method definition (`MOCK_METHOD`) in a `public:` -section of the mock class, regardless of the method being mocked being `public`, -`protected`, or `private` in the base class. This allows `ON_CALL` and -`EXPECT_CALL` to reference the mock function from outside of the mock class. -(Yes, C++ allows a subclass to change the access level of a virtual function in -the base class.) Example: - -```cpp -class Foo { - public: - ... - virtual bool Transform(Gadget* g) = 0; - - protected: - virtual void Resume(); - - private: - virtual int GetTimeOut(); -}; - -class MockFoo : public Foo { - public: - ... - MOCK_METHOD(bool, Transform, (Gadget* g), (override)); - - // The following must be in the public section, even though the - // methods are protected or private in the base class. - MOCK_METHOD(void, Resume, (), (override)); - MOCK_METHOD(int, GetTimeOut, (), (override)); -}; -``` - -### Mocking Overloaded Methods - -You can mock overloaded functions as usual. No special attention is required: - -```cpp -class Foo { - ... - - // Must be virtual as we'll inherit from Foo. - virtual ~Foo(); - - // Overloaded on the types and/or numbers of arguments. - virtual int Add(Element x); - virtual int Add(int times, Element x); - - // Overloaded on the const-ness of this object. - virtual Bar& GetBar(); - virtual const Bar& GetBar() const; -}; - -class MockFoo : public Foo { - ... - MOCK_METHOD(int, Add, (Element x), (override)); - MOCK_METHOD(int, Add, (int times, Element x), (override)); - - MOCK_METHOD(Bar&, GetBar, (), (override)); - MOCK_METHOD(const Bar&, GetBar, (), (const, override)); -}; -``` - -**Note:** if you don't mock all versions of the overloaded method, the compiler -will give you a warning about some methods in the base class being hidden. To -fix that, use `using` to bring them in scope: - -```cpp -class MockFoo : public Foo { - ... - using Foo::Add; - MOCK_METHOD(int, Add, (Element x), (override)); - // We don't want to mock int Add(int times, Element x); - ... -}; -``` - -### Mocking Class Templates - -You can mock class templates just like any class. - -```cpp -template <typename Elem> -class StackInterface { - ... - // Must be virtual as we'll inherit from StackInterface. - virtual ~StackInterface(); - - virtual int GetSize() const = 0; - virtual void Push(const Elem& x) = 0; -}; - -template <typename Elem> -class MockStack : public StackInterface<Elem> { - ... - MOCK_METHOD(int, GetSize, (), (override)); - MOCK_METHOD(void, Push, (const Elem& x), (override)); -}; -``` - -### Mocking Non-virtual Methods {#MockingNonVirtualMethods} - -gMock can mock non-virtual functions to be used in Hi-perf dependency -injection.<!-- GOOGLETEST_CM0017 DO NOT DELETE --> - -In this case, instead of sharing a common base class with the real class, your -mock class will be *unrelated* to the real class, but contain methods with the -same signatures. The syntax for mocking non-virtual methods is the *same* as -mocking virtual methods (just don't add `override`): - -```cpp -// A simple packet stream class. None of its members is virtual. -class ConcretePacketStream { - public: - void AppendPacket(Packet* new_packet); - const Packet* GetPacket(size_t packet_number) const; - size_t NumberOfPackets() const; - ... -}; - -// A mock packet stream class. It inherits from no other, but defines -// GetPacket() and NumberOfPackets(). -class MockPacketStream { - public: - MOCK_METHOD(const Packet*, GetPacket, (size_t packet_number), (const)); - MOCK_METHOD(size_t, NumberOfPackets, (), (const)); - ... -}; -``` - -Note that the mock class doesn't define `AppendPacket()`, unlike the real class. -That's fine as long as the test doesn't need to call it. - -Next, you need a way to say that you want to use `ConcretePacketStream` in -production code, and use `MockPacketStream` in tests. Since the functions are -not virtual and the two classes are unrelated, you must specify your choice at -*compile time* (as opposed to run time). - -One way to do it is to templatize your code that needs to use a packet stream. -More specifically, you will give your code a template type argument for the type -of the packet stream. In production, you will instantiate your template with -`ConcretePacketStream` as the type argument. In tests, you will instantiate the -same template with `MockPacketStream`. For example, you may write: - -```cpp -template <class PacketStream> -void CreateConnection(PacketStream* stream) { ... } - -template <class PacketStream> -class PacketReader { - public: - void ReadPackets(PacketStream* stream, size_t packet_num); -}; -``` - -Then you can use `CreateConnection<ConcretePacketStream>()` and -`PacketReader<ConcretePacketStream>` in production code, and use -`CreateConnection<MockPacketStream>()` and `PacketReader<MockPacketStream>` in -tests. - -```cpp - MockPacketStream mock_stream; - EXPECT_CALL(mock_stream, ...)...; - .. set more expectations on mock_stream ... - PacketReader<MockPacketStream> reader(&mock_stream); - ... exercise reader ... -``` - -### Mocking Free Functions - -It's possible to use gMock to mock a free function (i.e. a C-style function or a -static method). You just need to rewrite your code to use an interface (abstract -class). - -Instead of calling a free function (say, `OpenFile`) directly, introduce an -interface for it and have a concrete subclass that calls the free function: - -```cpp -class FileInterface { - public: - ... - virtual bool Open(const char* path, const char* mode) = 0; -}; - -class File : public FileInterface { - public: - ... - virtual bool Open(const char* path, const char* mode) { - return OpenFile(path, mode); - } -}; -``` - -Your code should talk to `FileInterface` to open a file. Now it's easy to mock -out the function. - -This may seem like a lot of hassle, but in practice you often have multiple -related functions that you can put in the same interface, so the per-function -syntactic overhead will be much lower. - -If you are concerned about the performance overhead incurred by virtual -functions, and profiling confirms your concern, you can combine this with the -recipe for [mocking non-virtual methods](#MockingNonVirtualMethods). - -### Old-Style `MOCK_METHODn` Macros - -Before the generic `MOCK_METHOD` macro -[was introduced in 2018](https://github.com/google/googletest/commit/c5f08bf91944ce1b19bcf414fa1760e69d20afc2), -mocks where created using a family of macros collectively called `MOCK_METHODn`. -These macros are still supported, though migration to the new `MOCK_METHOD` is -recommended. - -The macros in the `MOCK_METHODn` family differ from `MOCK_METHOD`: - -* The general structure is `MOCK_METHODn(MethodName, ReturnType(Args))`, - instead of `MOCK_METHOD(ReturnType, MethodName, (Args))`. -* The number `n` must equal the number of arguments. -* When mocking a const method, one must use `MOCK_CONST_METHODn`. -* When mocking a class template, the macro name must be suffixed with `_T`. -* In order to specify the call type, the macro name must be suffixed with - `_WITH_CALLTYPE`, and the call type is the first macro argument. - -Old macros and their new equivalents: - -<a name="table99"></a> -<table border="1" cellspacing="0" cellpadding="1"> -<tr> <th colspan=2> Simple </th></tr> -<tr> <td> Old </td> <td> `MOCK_METHOD1(Foo, bool(int))` </td> </tr> -<tr> <td> New </td> <td> `MOCK_METHOD(bool, Foo, (int))` </td> </tr> - -<tr> <th colspan=2> Const Method </th></tr> <tr> <td> Old </td> <td> -`MOCK_CONST_METHOD1(Foo, bool(int))` </td> </tr> <tr> <td> New </td> <td> -`MOCK_METHOD(bool, Foo, (int), (const))` </td> </tr> - -<tr> <th colspan=2> Method in a Class Template </th></tr> <tr> <td> Old </td> -<td> `MOCK_METHOD1_T(Foo, bool(int))` </td> </tr> <tr> <td> New </td> <td> -`MOCK_METHOD(bool, Foo, (int))` </td> </tr> - -<tr> <th colspan=2> Const Method in a Class Template </th></tr> <tr> <td> Old -</td> <td> `MOCK_CONST_METHOD1_T(Foo, bool(int))` </td> </tr> <tr> <td> New -</td> <td> `MOCK_METHOD(bool, Foo, (int), (const))` </td> </tr> - -<tr> <th colspan=2> Method with Call Type </th></tr> <tr> <td> Old </td> <td> -`MOCK_METHOD1_WITH_CALLTYPE(STDMETHODCALLTYPE, Foo, bool(int))` </td> </tr> <tr> -<td> New </td> <td> `MOCK_METHOD(bool, Foo, (int), -(Calltype(STDMETHODCALLTYPE)))` </td> </tr> - -<tr> <th colspan=2> Const Method with Call Type </th></tr> <tr> <td> Old</td> -<td> `MOCK_CONST_METHOD1_WITH_CALLTYPE(STDMETHODCALLTYPE, Foo, bool(int))` </td> -</tr> <tr> <td> New </td> <td> `MOCK_METHOD(bool, Foo, (int), (const, -Calltype(STDMETHODCALLTYPE)))` </td> </tr> - -<tr> <th colspan=2> Method with Call Type in a Class Template </th></tr> <tr> -<td> Old </td> <td> `MOCK_METHOD1_T_WITH_CALLTYPE(STDMETHODCALLTYPE, Foo, -bool(int))` </td> </tr> <tr> <td> New </td> <td> `MOCK_METHOD(bool, Foo, (int), -(Calltype(STDMETHODCALLTYPE)))` </td> </tr> - -<tr> <th colspan=2> Const Method with Call Type in a Class Template </th></tr> -<tr> <td> Old </td> <td> `MOCK_CONST_METHOD1_T_WITH_CALLTYPE(STDMETHODCALLTYPE, -Foo, bool(int))` </td> </tr> <tr> <td> New </td> <td> `MOCK_METHOD(bool, Foo, -(int), (const, Calltype(STDMETHODCALLTYPE)))` </td> </tr> - -</table> - -### The Nice, the Strict, and the Naggy {#NiceStrictNaggy} - -If a mock method has no `EXPECT_CALL` spec but is called, we say that it's an -"uninteresting call", and the default action (which can be specified using -`ON_CALL()`) of the method will be taken. Currently, an uninteresting call will -also by default cause gMock to print a warning. (In the future, we might remove -this warning by default.) - -However, sometimes you may want to ignore these uninteresting calls, and -sometimes you may want to treat them as errors. gMock lets you make the decision -on a per-mock-object basis. - -Suppose your test uses a mock class `MockFoo`: - -```cpp -TEST(...) { - MockFoo mock_foo; - EXPECT_CALL(mock_foo, DoThis()); - ... code that uses mock_foo ... -} -``` - -If a method of `mock_foo` other than `DoThis()` is called, you will get a -warning. However, if you rewrite your test to use `NiceMock<MockFoo>` instead, -you can suppress the warning: - -```cpp -using ::testing::NiceMock; - -TEST(...) { - NiceMock<MockFoo> mock_foo; - EXPECT_CALL(mock_foo, DoThis()); - ... code that uses mock_foo ... -} -``` - -`NiceMock<MockFoo>` is a subclass of `MockFoo`, so it can be used wherever -`MockFoo` is accepted. - -It also works if `MockFoo`'s constructor takes some arguments, as -`NiceMock<MockFoo>` "inherits" `MockFoo`'s constructors: - -```cpp -using ::testing::NiceMock; - -TEST(...) { - NiceMock<MockFoo> mock_foo(5, "hi"); // Calls MockFoo(5, "hi"). - EXPECT_CALL(mock_foo, DoThis()); - ... code that uses mock_foo ... -} -``` - -The usage of `StrictMock` is similar, except that it makes all uninteresting -calls failures: - -```cpp -using ::testing::StrictMock; - -TEST(...) { - StrictMock<MockFoo> mock_foo; - EXPECT_CALL(mock_foo, DoThis()); - ... code that uses mock_foo ... - - // The test will fail if a method of mock_foo other than DoThis() - // is called. -} -``` - -NOTE: `NiceMock` and `StrictMock` only affects *uninteresting* calls (calls of -*methods* with no expectations); they do not affect *unexpected* calls (calls of -methods with expectations, but they don't match). See -[Understanding Uninteresting vs Unexpected Calls](#uninteresting-vs-unexpected). - -There are some caveats though (sadly they are side effects of C++'s -limitations): - -1. `NiceMock<MockFoo>` and `StrictMock<MockFoo>` only work for mock methods - defined using the `MOCK_METHOD` macro **directly** in the `MockFoo` class. - If a mock method is defined in a **base class** of `MockFoo`, the "nice" or - "strict" modifier may not affect it, depending on the compiler. In - particular, nesting `NiceMock` and `StrictMock` (e.g. - `NiceMock<StrictMock<MockFoo> >`) is **not** supported. -2. `NiceMock<MockFoo>` and `StrictMock<MockFoo>` may not work correctly if the - destructor of `MockFoo` is not virtual. We would like to fix this, but it - requires cleaning up existing tests. - -Finally, you should be **very cautious** about when to use naggy or strict -mocks, as they tend to make tests more brittle and harder to maintain. When you -refactor your code without changing its externally visible behavior, ideally you -shouldn't need to update any tests. If your code interacts with a naggy mock, -however, you may start to get spammed with warnings as the result of your -change. Worse, if your code interacts with a strict mock, your tests may start -to fail and you'll be forced to fix them. Our general recommendation is to use -nice mocks (not yet the default) most of the time, use naggy mocks (the current -default) when developing or debugging tests, and use strict mocks only as the -last resort. - -### Simplifying the Interface without Breaking Existing Code {#SimplerInterfaces} - -Sometimes a method has a long list of arguments that is mostly uninteresting. -For example: - -```cpp -class LogSink { - public: - ... - virtual void send(LogSeverity severity, const char* full_filename, - const char* base_filename, int line, - const struct tm* tm_time, - const char* message, size_t message_len) = 0; -}; -``` - -This method's argument list is lengthy and hard to work with (the `message` -argument is not even 0-terminated). If we mock it as is, using the mock will be -awkward. If, however, we try to simplify this interface, we'll need to fix all -clients depending on it, which is often infeasible. - -The trick is to redispatch the method in the mock class: - -```cpp -class ScopedMockLog : public LogSink { - public: - ... - virtual void send(LogSeverity severity, const char* full_filename, - const char* base_filename, int line, const tm* tm_time, - const char* message, size_t message_len) { - // We are only interested in the log severity, full file name, and - // log message. - Log(severity, full_filename, std::string(message, message_len)); - } - - // Implements the mock method: - // - // void Log(LogSeverity severity, - // const string& file_path, - // const string& message); - MOCK_METHOD(void, Log, - (LogSeverity severity, const string& file_path, - const string& message)); -}; -``` - -By defining a new mock method with a trimmed argument list, we make the mock -class more user-friendly. - -This technique may also be applied to make overloaded methods more amenable to -mocking. For example, when overloads have been used to implement default -arguments: - -```cpp -class MockTurtleFactory : public TurtleFactory { - public: - Turtle* MakeTurtle(int length, int weight) override { ... } - Turtle* MakeTurtle(int length, int weight, int speed) override { ... } - - // the above methods delegate to this one: - MOCK_METHOD(Turtle*, DoMakeTurtle, ()); -}; -``` - -This allows tests that don't care which overload was invoked to avoid specifying -argument matchers: - -```cpp -ON_CALL(factory, DoMakeTurtle) - .WillByDefault(Return(MakeMockTurtle())); -``` - -### Alternative to Mocking Concrete Classes - -Often you may find yourself using classes that don't implement interfaces. In -order to test your code that uses such a class (let's call it `Concrete`), you -may be tempted to make the methods of `Concrete` virtual and then mock it. - -Try not to do that. - -Making a non-virtual function virtual is a big decision. It creates an extension -point where subclasses can tweak your class' behavior. This weakens your control -on the class because now it's harder to maintain the class invariants. You -should make a function virtual only when there is a valid reason for a subclass -to override it. - -Mocking concrete classes directly is problematic as it creates a tight coupling -between the class and the tests - any small change in the class may invalidate -your tests and make test maintenance a pain. - -To avoid such problems, many programmers have been practicing "coding to -interfaces": instead of talking to the `Concrete` class, your code would define -an interface and talk to it. Then you implement that interface as an adaptor on -top of `Concrete`. In tests, you can easily mock that interface to observe how -your code is doing. - -This technique incurs some overhead: - -* You pay the cost of virtual function calls (usually not a problem). -* There is more abstraction for the programmers to learn. - -However, it can also bring significant benefits in addition to better -testability: - -* `Concrete`'s API may not fit your problem domain very well, as you may not - be the only client it tries to serve. By designing your own interface, you - have a chance to tailor it to your need - you may add higher-level - functionalities, rename stuff, etc instead of just trimming the class. This - allows you to write your code (user of the interface) in a more natural way, - which means it will be more readable, more maintainable, and you'll be more - productive. -* If `Concrete`'s implementation ever has to change, you don't have to rewrite - everywhere it is used. Instead, you can absorb the change in your - implementation of the interface, and your other code and tests will be - insulated from this change. - -Some people worry that if everyone is practicing this technique, they will end -up writing lots of redundant code. This concern is totally understandable. -However, there are two reasons why it may not be the case: - -* Different projects may need to use `Concrete` in different ways, so the best - interfaces for them will be different. Therefore, each of them will have its - own domain-specific interface on top of `Concrete`, and they will not be the - same code. -* If enough projects want to use the same interface, they can always share it, - just like they have been sharing `Concrete`. You can check in the interface - and the adaptor somewhere near `Concrete` (perhaps in a `contrib` - sub-directory) and let many projects use it. - -You need to weigh the pros and cons carefully for your particular problem, but -I'd like to assure you that the Java community has been practicing this for a -long time and it's a proven effective technique applicable in a wide variety of -situations. :-) - -### Delegating Calls to a Fake {#DelegatingToFake} - -Some times you have a non-trivial fake implementation of an interface. For -example: - -```cpp -class Foo { - public: - virtual ~Foo() {} - virtual char DoThis(int n) = 0; - virtual void DoThat(const char* s, int* p) = 0; -}; - -class FakeFoo : public Foo { - public: - char DoThis(int n) override { - return (n > 0) ? '+' : - (n < 0) ? '-' : '0'; - } - - void DoThat(const char* s, int* p) override { - *p = strlen(s); - } -}; -``` - -Now you want to mock this interface such that you can set expectations on it. -However, you also want to use `FakeFoo` for the default behavior, as duplicating -it in the mock object is, well, a lot of work. - -When you define the mock class using gMock, you can have it delegate its default -action to a fake class you already have, using this pattern: - -```cpp -class MockFoo : public Foo { - public: - // Normal mock method definitions using gMock. - MOCK_METHOD(char, DoThis, (int n), (override)); - MOCK_METHOD(void, DoThat, (const char* s, int* p), (override)); - - // Delegates the default actions of the methods to a FakeFoo object. - // This must be called *before* the custom ON_CALL() statements. - void DelegateToFake() { - ON_CALL(*this, DoThis).WillByDefault([this](int n) { - return fake_.DoThis(n); - }); - ON_CALL(*this, DoThat).WillByDefault([this](const char* s, int* p) { - fake_.DoThat(s, p); - }); - } - - private: - FakeFoo fake_; // Keeps an instance of the fake in the mock. -}; -``` - -With that, you can use `MockFoo` in your tests as usual. Just remember that if -you don't explicitly set an action in an `ON_CALL()` or `EXPECT_CALL()`, the -fake will be called upon to do it.: - -```cpp -using ::testing::_; - -TEST(AbcTest, Xyz) { - MockFoo foo; - - foo.DelegateToFake(); // Enables the fake for delegation. - - // Put your ON_CALL(foo, ...)s here, if any. - - // No action specified, meaning to use the default action. - EXPECT_CALL(foo, DoThis(5)); - EXPECT_CALL(foo, DoThat(_, _)); - - int n = 0; - EXPECT_EQ('+', foo.DoThis(5)); // FakeFoo::DoThis() is invoked. - foo.DoThat("Hi", &n); // FakeFoo::DoThat() is invoked. - EXPECT_EQ(2, n); -} -``` - -**Some tips:** - -* If you want, you can still override the default action by providing your own - `ON_CALL()` or using `.WillOnce()` / `.WillRepeatedly()` in `EXPECT_CALL()`. -* In `DelegateToFake()`, you only need to delegate the methods whose fake - implementation you intend to use. - -* The general technique discussed here works for overloaded methods, but - you'll need to tell the compiler which version you mean. To disambiguate a - mock function (the one you specify inside the parentheses of `ON_CALL()`), - use [this technique](#SelectOverload); to disambiguate a fake function (the - one you place inside `Invoke()`), use a `static_cast` to specify the - function's type. For instance, if class `Foo` has methods `char DoThis(int - n)` and `bool DoThis(double x) const`, and you want to invoke the latter, - you need to write `Invoke(&fake_, static_cast<bool (FakeFoo::*)(double) - const>(&FakeFoo::DoThis))` instead of `Invoke(&fake_, &FakeFoo::DoThis)` - (The strange-looking thing inside the angled brackets of `static_cast` is - the type of a function pointer to the second `DoThis()` method.). - -* Having to mix a mock and a fake is often a sign of something gone wrong. - Perhaps you haven't got used to the interaction-based way of testing yet. Or - perhaps your interface is taking on too many roles and should be split up. - Therefore, **don't abuse this**. We would only recommend to do it as an - intermediate step when you are refactoring your code. - -Regarding the tip on mixing a mock and a fake, here's an example on why it may -be a bad sign: Suppose you have a class `System` for low-level system -operations. In particular, it does file and I/O operations. And suppose you want -to test how your code uses `System` to do I/O, and you just want the file -operations to work normally. If you mock out the entire `System` class, you'll -have to provide a fake implementation for the file operation part, which -suggests that `System` is taking on too many roles. - -Instead, you can define a `FileOps` interface and an `IOOps` interface and split -`System`'s functionalities into the two. Then you can mock `IOOps` without -mocking `FileOps`. - -### Delegating Calls to a Real Object - -When using testing doubles (mocks, fakes, stubs, and etc), sometimes their -behaviors will differ from those of the real objects. This difference could be -either intentional (as in simulating an error such that you can test the error -handling code) or unintentional. If your mocks have different behaviors than the -real objects by mistake, you could end up with code that passes the tests but -fails in production. - -You can use the *delegating-to-real* technique to ensure that your mock has the -same behavior as the real object while retaining the ability to validate calls. -This technique is very similar to the [delegating-to-fake](#DelegatingToFake) -technique, the difference being that we use a real object instead of a fake. -Here's an example: - -```cpp -using ::testing::AtLeast; - -class MockFoo : public Foo { - public: - MockFoo() { - // By default, all calls are delegated to the real object. - ON_CALL(*this, DoThis).WillByDefault([this](int n) { - return real_.DoThis(n); - }); - ON_CALL(*this, DoThat).WillByDefault([this](const char* s, int* p) { - real_.DoThat(s, p); - }); - ... - } - MOCK_METHOD(char, DoThis, ...); - MOCK_METHOD(void, DoThat, ...); - ... - private: - Foo real_; -}; - -... - MockFoo mock; - EXPECT_CALL(mock, DoThis()) - .Times(3); - EXPECT_CALL(mock, DoThat("Hi")) - .Times(AtLeast(1)); - ... use mock in test ... -``` - -With this, gMock will verify that your code made the right calls (with the right -arguments, in the right order, called the right number of times, etc), and a -real object will answer the calls (so the behavior will be the same as in -production). This gives you the best of both worlds. - -### Delegating Calls to a Parent Class - -Ideally, you should code to interfaces, whose methods are all pure virtual. In -reality, sometimes you do need to mock a virtual method that is not pure (i.e, -it already has an implementation). For example: - -```cpp -class Foo { - public: - virtual ~Foo(); - - virtual void Pure(int n) = 0; - virtual int Concrete(const char* str) { ... } -}; - -class MockFoo : public Foo { - public: - // Mocking a pure method. - MOCK_METHOD(void, Pure, (int n), (override)); - // Mocking a concrete method. Foo::Concrete() is shadowed. - MOCK_METHOD(int, Concrete, (const char* str), (override)); -}; -``` - -Sometimes you may want to call `Foo::Concrete()` instead of -`MockFoo::Concrete()`. Perhaps you want to do it as part of a stub action, or -perhaps your test doesn't need to mock `Concrete()` at all (but it would be -oh-so painful to have to define a new mock class whenever you don't need to mock -one of its methods). - -You can call `Foo::Concrete()` inside an action by: - -```cpp -... - EXPECT_CALL(foo, Concrete).WillOnce([&foo](const char* str) { - return foo.Foo::Concrete(str); - }); -``` - -or tell the mock object that you don't want to mock `Concrete()`: - -```cpp -... - ON_CALL(foo, Concrete).WillByDefault([&foo](const char* str) { - return foo.Foo::Concrete(str); - }); -``` - -(Why don't we just write `{ return foo.Concrete(str); }`? If you do that, -`MockFoo::Concrete()` will be called (and cause an infinite recursion) since -`Foo::Concrete()` is virtual. That's just how C++ works.) - -## Using Matchers - -### Matching Argument Values Exactly - -You can specify exactly which arguments a mock method is expecting: - -```cpp -using ::testing::Return; -... - EXPECT_CALL(foo, DoThis(5)) - .WillOnce(Return('a')); - EXPECT_CALL(foo, DoThat("Hello", bar)); -``` - -### Using Simple Matchers - -You can use matchers to match arguments that have a certain property: - -```cpp -using ::testing::NotNull; -using ::testing::Return; -... - EXPECT_CALL(foo, DoThis(Ge(5))) // The argument must be >= 5. - .WillOnce(Return('a')); - EXPECT_CALL(foo, DoThat("Hello", NotNull())); - // The second argument must not be NULL. -``` - -A frequently used matcher is `_`, which matches anything: - -```cpp - EXPECT_CALL(foo, DoThat(_, NotNull())); -``` -<!-- GOOGLETEST_CM0022 DO NOT DELETE --> - -### Combining Matchers {#CombiningMatchers} - -You can build complex matchers from existing ones using `AllOf()`, -`AllOfArray()`, `AnyOf()`, `AnyOfArray()` and `Not()`: - -```cpp -using ::testing::AllOf; -using ::testing::Gt; -using ::testing::HasSubstr; -using ::testing::Ne; -using ::testing::Not; -... - // The argument must be > 5 and != 10. - EXPECT_CALL(foo, DoThis(AllOf(Gt(5), - Ne(10)))); - - // The first argument must not contain sub-string "blah". - EXPECT_CALL(foo, DoThat(Not(HasSubstr("blah")), - NULL)); -``` - -Matchers are function objects, and parametrized matchers can be composed just -like any other function. However because their types can be long and rarely -provide meaningful information, it can be easier to express them with C++14 -generic lambdas to avoid specifying types. For example, - -```cpp -using ::testing::Contains; -using ::testing::Property; - -inline constexpr auto HasFoo = [](const auto& f) { - return Property(&MyClass::foo, Contains(f)); -}; -... - EXPECT_THAT(x, HasFoo("blah")); -``` - -### Casting Matchers {#SafeMatcherCast} - -gMock matchers are statically typed, meaning that the compiler can catch your -mistake if you use a matcher of the wrong type (for example, if you use `Eq(5)` -to match a `string` argument). Good for you! - -Sometimes, however, you know what you're doing and want the compiler to give you -some slack. One example is that you have a matcher for `long` and the argument -you want to match is `int`. While the two types aren't exactly the same, there -is nothing really wrong with using a `Matcher<long>` to match an `int` - after -all, we can first convert the `int` argument to a `long` losslessly before -giving it to the matcher. - -To support this need, gMock gives you the `SafeMatcherCast<T>(m)` function. It -casts a matcher `m` to type `Matcher<T>`. To ensure safety, gMock checks that -(let `U` be the type `m` accepts : - -1. Type `T` can be *implicitly* cast to type `U`; -2. When both `T` and `U` are built-in arithmetic types (`bool`, integers, and - floating-point numbers), the conversion from `T` to `U` is not lossy (in - other words, any value representable by `T` can also be represented by `U`); - and -3. When `U` is a reference, `T` must also be a reference (as the underlying - matcher may be interested in the address of the `U` value). - -The code won't compile if any of these conditions isn't met. - -Here's one example: - -```cpp -using ::testing::SafeMatcherCast; - -// A base class and a child class. -class Base { ... }; -class Derived : public Base { ... }; - -class MockFoo : public Foo { - public: - MOCK_METHOD(void, DoThis, (Derived* derived), (override)); -}; - -... - MockFoo foo; - // m is a Matcher<Base*> we got from somewhere. - EXPECT_CALL(foo, DoThis(SafeMatcherCast<Derived*>(m))); -``` - -If you find `SafeMatcherCast<T>(m)` too limiting, you can use a similar function -`MatcherCast<T>(m)`. The difference is that `MatcherCast` works as long as you -can `static_cast` type `T` to type `U`. - -`MatcherCast` essentially lets you bypass C++'s type system (`static_cast` isn't -always safe as it could throw away information, for example), so be careful not -to misuse/abuse it. - -### Selecting Between Overloaded Functions {#SelectOverload} - -If you expect an overloaded function to be called, the compiler may need some -help on which overloaded version it is. - -To disambiguate functions overloaded on the const-ness of this object, use the -`Const()` argument wrapper. - -```cpp -using ::testing::ReturnRef; - -class MockFoo : public Foo { - ... - MOCK_METHOD(Bar&, GetBar, (), (override)); - MOCK_METHOD(const Bar&, GetBar, (), (const, override)); -}; - -... - MockFoo foo; - Bar bar1, bar2; - EXPECT_CALL(foo, GetBar()) // The non-const GetBar(). - .WillOnce(ReturnRef(bar1)); - EXPECT_CALL(Const(foo), GetBar()) // The const GetBar(). - .WillOnce(ReturnRef(bar2)); -``` - -(`Const()` is defined by gMock and returns a `const` reference to its argument.) - -To disambiguate overloaded functions with the same number of arguments but -different argument types, you may need to specify the exact type of a matcher, -either by wrapping your matcher in `Matcher<type>()`, or using a matcher whose -type is fixed (`TypedEq<type>`, `An<type>()`, etc): - -```cpp -using ::testing::An; -using ::testing::Matcher; -using ::testing::TypedEq; - -class MockPrinter : public Printer { - public: - MOCK_METHOD(void, Print, (int n), (override)); - MOCK_METHOD(void, Print, (char c), (override)); -}; - -TEST(PrinterTest, Print) { - MockPrinter printer; - - EXPECT_CALL(printer, Print(An<int>())); // void Print(int); - EXPECT_CALL(printer, Print(Matcher<int>(Lt(5)))); // void Print(int); - EXPECT_CALL(printer, Print(TypedEq<char>('a'))); // void Print(char); - - printer.Print(3); - printer.Print(6); - printer.Print('a'); -} -``` - -### Performing Different Actions Based on the Arguments - -When a mock method is called, the *last* matching expectation that's still -active will be selected (think "newer overrides older"). So, you can make a -method do different things depending on its argument values like this: - -```cpp -using ::testing::_; -using ::testing::Lt; -using ::testing::Return; -... - // The default case. - EXPECT_CALL(foo, DoThis(_)) - .WillRepeatedly(Return('b')); - // The more specific case. - EXPECT_CALL(foo, DoThis(Lt(5))) - .WillRepeatedly(Return('a')); -``` - -Now, if `foo.DoThis()` is called with a value less than 5, `'a'` will be -returned; otherwise `'b'` will be returned. - -### Matching Multiple Arguments as a Whole - -Sometimes it's not enough to match the arguments individually. For example, we -may want to say that the first argument must be less than the second argument. -The `With()` clause allows us to match all arguments of a mock function as a -whole. For example, - -```cpp -using ::testing::_; -using ::testing::Ne; -using ::testing::Lt; -... - EXPECT_CALL(foo, InRange(Ne(0), _)) - .With(Lt()); -``` - -says that the first argument of `InRange()` must not be 0, and must be less than -the second argument. - -The expression inside `With()` must be a matcher of type `Matcher<std::tuple<A1, -..., An>>`, where `A1`, ..., `An` are the types of the function arguments. - -You can also write `AllArgs(m)` instead of `m` inside `.With()`. The two forms -are equivalent, but `.With(AllArgs(Lt()))` is more readable than `.With(Lt())`. - -You can use `Args<k1, ..., kn>(m)` to match the `n` selected arguments (as a -tuple) against `m`. For example, - -```cpp -using ::testing::_; -using ::testing::AllOf; -using ::testing::Args; -using ::testing::Lt; -... - EXPECT_CALL(foo, Blah) - .With(AllOf(Args<0, 1>(Lt()), Args<1, 2>(Lt()))); -``` - -says that `Blah` will be called with arguments `x`, `y`, and `z` where `x < y < -z`. Note that in this example, it wasn't necessary specify the positional -matchers. - -As a convenience and example, gMock provides some matchers for 2-tuples, -including the `Lt()` matcher above. See [here](#MultiArgMatchers) for the -complete list. - -Note that if you want to pass the arguments to a predicate of your own (e.g. -`.With(Args<0, 1>(Truly(&MyPredicate)))`), that predicate MUST be written to -take a `std::tuple` as its argument; gMock will pass the `n` selected arguments -as *one* single tuple to the predicate. - -### Using Matchers as Predicates - -Have you noticed that a matcher is just a fancy predicate that also knows how to -describe itself? Many existing algorithms take predicates as arguments (e.g. -those defined in STL's `<algorithm>` header), and it would be a shame if gMock -matchers were not allowed to participate. - -Luckily, you can use a matcher where a unary predicate functor is expected by -wrapping it inside the `Matches()` function. For example, - -```cpp -#include <algorithm> -#include <vector> - -using ::testing::Matches; -using ::testing::Ge; - -vector<int> v; -... -// How many elements in v are >= 10? -const int count = count_if(v.begin(), v.end(), Matches(Ge(10))); -``` - -Since you can build complex matchers from simpler ones easily using gMock, this -gives you a way to conveniently construct composite predicates (doing the same -using STL's `<functional>` header is just painful). For example, here's a -predicate that's satisfied by any number that is >= 0, <= 100, and != 50: - -```cpp -using testing::AllOf; -using testing::Ge; -using testing::Le; -using testing::Matches; -using testing::Ne; -... -Matches(AllOf(Ge(0), Le(100), Ne(50))) -``` - -### Using Matchers in googletest Assertions - -Since matchers are basically predicates that also know how to describe -themselves, there is a way to take advantage of them in googletest assertions. -It's called `ASSERT_THAT` and `EXPECT_THAT`: - -```cpp - ASSERT_THAT(value, matcher); // Asserts that value matches matcher. - EXPECT_THAT(value, matcher); // The non-fatal version. -``` - -For example, in a googletest test you can write: - -```cpp -#include "gmock/gmock.h" - -using ::testing::AllOf; -using ::testing::Ge; -using ::testing::Le; -using ::testing::MatchesRegex; -using ::testing::StartsWith; - -... - EXPECT_THAT(Foo(), StartsWith("Hello")); - EXPECT_THAT(Bar(), MatchesRegex("Line \\d+")); - ASSERT_THAT(Baz(), AllOf(Ge(5), Le(10))); -``` - -which (as you can probably guess) executes `Foo()`, `Bar()`, and `Baz()`, and -verifies that: - -* `Foo()` returns a string that starts with `"Hello"`. -* `Bar()` returns a string that matches regular expression `"Line \\d+"`. -* `Baz()` returns a number in the range [5, 10]. - -The nice thing about these macros is that *they read like English*. They -generate informative messages too. For example, if the first `EXPECT_THAT()` -above fails, the message will be something like: - -```cpp -Value of: Foo() - Actual: "Hi, world!" -Expected: starts with "Hello" -``` - -**Credit:** The idea of `(ASSERT|EXPECT)_THAT` was borrowed from Joe Walnes' -Hamcrest project, which adds `assertThat()` to JUnit. - -### Using Predicates as Matchers - -gMock provides a [built-in set](cheat_sheet.md#MatcherList) of matchers. In case -you find them lacking, you can use an arbitrary unary predicate function or -functor as a matcher - as long as the predicate accepts a value of the type you -want. You do this by wrapping the predicate inside the `Truly()` function, for -example: - -```cpp -using ::testing::Truly; - -int IsEven(int n) { return (n % 2) == 0 ? 1 : 0; } -... - // Bar() must be called with an even number. - EXPECT_CALL(foo, Bar(Truly(IsEven))); -``` - -Note that the predicate function / functor doesn't have to return `bool`. It -works as long as the return value can be used as the condition in in statement -`if (condition) ...`. - -<!-- GOOGLETEST_CM0023 DO NOT DELETE --> - -### Matching Arguments that Are Not Copyable - -When you do an `EXPECT_CALL(mock_obj, Foo(bar))`, gMock saves away a copy of -`bar`. When `Foo()` is called later, gMock compares the argument to `Foo()` with -the saved copy of `bar`. This way, you don't need to worry about `bar` being -modified or destroyed after the `EXPECT_CALL()` is executed. The same is true -when you use matchers like `Eq(bar)`, `Le(bar)`, and so on. - -But what if `bar` cannot be copied (i.e. has no copy constructor)? You could -define your own matcher function or callback and use it with `Truly()`, as the -previous couple of recipes have shown. Or, you may be able to get away from it -if you can guarantee that `bar` won't be changed after the `EXPECT_CALL()` is -executed. Just tell gMock that it should save a reference to `bar`, instead of a -copy of it. Here's how: - -```cpp -using ::testing::Eq; -using ::testing::Lt; -... - // Expects that Foo()'s argument == bar. - EXPECT_CALL(mock_obj, Foo(Eq(std::ref(bar)))); - - // Expects that Foo()'s argument < bar. - EXPECT_CALL(mock_obj, Foo(Lt(std::ref(bar)))); -``` - -Remember: if you do this, don't change `bar` after the `EXPECT_CALL()`, or the -result is undefined. - -### Validating a Member of an Object - -Often a mock function takes a reference to object as an argument. When matching -the argument, you may not want to compare the entire object against a fixed -object, as that may be over-specification. Instead, you may need to validate a -certain member variable or the result of a certain getter method of the object. -You can do this with `Field()` and `Property()`. More specifically, - -```cpp -Field(&Foo::bar, m) -``` - -is a matcher that matches a `Foo` object whose `bar` member variable satisfies -matcher `m`. - -```cpp -Property(&Foo::baz, m) -``` - -is a matcher that matches a `Foo` object whose `baz()` method returns a value -that satisfies matcher `m`. - -For example: - -<!-- mdformat off(github rendering does not support multiline tables) --> -| Expression | Description | -| :--------------------------- | :--------------------------------------- | -| `Field(&Foo::number, Ge(3))` | Matches `x` where `x.number >= 3`. | -| `Property(&Foo::name, StartsWith("John "))` | Matches `x` where `x.name()` starts with `"John "`. | -<!-- mdformat on --> - -Note that in `Property(&Foo::baz, ...)`, method `baz()` must take no argument -and be declared as `const`. - -BTW, `Field()` and `Property()` can also match plain pointers to objects. For -instance, - -```cpp -using ::testing::Field; -using ::testing::Ge; -... -Field(&Foo::number, Ge(3)) -``` - -matches a plain pointer `p` where `p->number >= 3`. If `p` is `NULL`, the match -will always fail regardless of the inner matcher. - -What if you want to validate more than one members at the same time? Remember -that there are [`AllOf()` and `AllOfArray()`](#CombiningMatchers). - -Finally `Field()` and `Property()` provide overloads that take the field or -property names as the first argument to include it in the error message. This -can be useful when creating combined matchers. - -```cpp -using ::testing::AllOf; -using ::testing::Field; -using ::testing::Matcher; -using ::testing::SafeMatcherCast; - -Matcher<Foo> IsFoo(const Foo& foo) { - return AllOf(Field("some_field", &Foo::some_field, foo.some_field), - Field("other_field", &Foo::other_field, foo.other_field), - Field("last_field", &Foo::last_field, foo.last_field)); -} -``` - -### Validating the Value Pointed to by a Pointer Argument - -C++ functions often take pointers as arguments. You can use matchers like -`IsNull()`, `NotNull()`, and other comparison matchers to match a pointer, but -what if you want to make sure the value *pointed to* by the pointer, instead of -the pointer itself, has a certain property? Well, you can use the `Pointee(m)` -matcher. - -`Pointee(m)` matches a pointer if and only if `m` matches the value the pointer -points to. For example: - -```cpp -using ::testing::Ge; -using ::testing::Pointee; -... - EXPECT_CALL(foo, Bar(Pointee(Ge(3)))); -``` - -expects `foo.Bar()` to be called with a pointer that points to a value greater -than or equal to 3. - -One nice thing about `Pointee()` is that it treats a `NULL` pointer as a match -failure, so you can write `Pointee(m)` instead of - -```cpp -using ::testing::AllOf; -using ::testing::NotNull; -using ::testing::Pointee; -... - AllOf(NotNull(), Pointee(m)) -``` - -without worrying that a `NULL` pointer will crash your test. - -Also, did we tell you that `Pointee()` works with both raw pointers **and** -smart pointers (`std::unique_ptr`, `std::shared_ptr`, etc)? - -What if you have a pointer to pointer? You guessed it - you can use nested -`Pointee()` to probe deeper inside the value. For example, -`Pointee(Pointee(Lt(3)))` matches a pointer that points to a pointer that points -to a number less than 3 (what a mouthful...). - -### Testing a Certain Property of an Object - -Sometimes you want to specify that an object argument has a certain property, -but there is no existing matcher that does this. If you want good error -messages, you should [define a matcher](#NewMatchers). If you want to do it -quick and dirty, you could get away with writing an ordinary function. - -Let's say you have a mock function that takes an object of type `Foo`, which has -an `int bar()` method and an `int baz()` method, and you want to constrain that -the argument's `bar()` value plus its `baz()` value is a given number. Here's -how you can define a matcher to do it: - -```cpp -using ::testing::Matcher; -using ::testing::MatcherInterface; -using ::testing::MatchResultListener; - -class BarPlusBazEqMatcher : public MatcherInterface<const Foo&> { - public: - explicit BarPlusBazEqMatcher(int expected_sum) - : expected_sum_(expected_sum) {} - - bool MatchAndExplain(const Foo& foo, - MatchResultListener* /* listener */) const override { - return (foo.bar() + foo.baz()) == expected_sum_; - } - - void DescribeTo(std::ostream* os) const override { - *os << "bar() + baz() equals " << expected_sum_; - } - - void DescribeNegationTo(std::ostream* os) const override { - *os << "bar() + baz() does not equal " << expected_sum_; - } - private: - const int expected_sum_; -}; - -Matcher<const Foo&> BarPlusBazEq(int expected_sum) { - return MakeMatcher(new BarPlusBazEqMatcher(expected_sum)); -} - -... - EXPECT_CALL(..., DoThis(BarPlusBazEq(5)))...; -``` - -### Matching Containers - -Sometimes an STL container (e.g. list, vector, map, ...) is passed to a mock -function and you may want to validate it. Since most STL containers support the -`==` operator, you can write `Eq(expected_container)` or simply -`expected_container` to match a container exactly. - -Sometimes, though, you may want to be more flexible (for example, the first -element must be an exact match, but the second element can be any positive -number, and so on). Also, containers used in tests often have a small number of -elements, and having to define the expected container out-of-line is a bit of a -hassle. - -You can use the `ElementsAre()` or `UnorderedElementsAre()` matcher in such -cases: - -```cpp -using ::testing::_; -using ::testing::ElementsAre; -using ::testing::Gt; -... - MOCK_METHOD(void, Foo, (const vector<int>& numbers), (override)); -... - EXPECT_CALL(mock, Foo(ElementsAre(1, Gt(0), _, 5))); -``` - -The above matcher says that the container must have 4 elements, which must be 1, -greater than 0, anything, and 5 respectively. - -If you instead write: - -```cpp -using ::testing::_; -using ::testing::Gt; -using ::testing::UnorderedElementsAre; -... - MOCK_METHOD(void, Foo, (const vector<int>& numbers), (override)); -... - EXPECT_CALL(mock, Foo(UnorderedElementsAre(1, Gt(0), _, 5))); -``` - -It means that the container must have 4 elements, which (under some permutation) -must be 1, greater than 0, anything, and 5 respectively. - -As an alternative you can place the arguments in a C-style array and use -`ElementsAreArray()` or `UnorderedElementsAreArray()` instead: - -```cpp -using ::testing::ElementsAreArray; -... - // ElementsAreArray accepts an array of element values. - const int expected_vector1[] = {1, 5, 2, 4, ...}; - EXPECT_CALL(mock, Foo(ElementsAreArray(expected_vector1))); - - // Or, an array of element matchers. - Matcher<int> expected_vector2[] = {1, Gt(2), _, 3, ...}; - EXPECT_CALL(mock, Foo(ElementsAreArray(expected_vector2))); -``` - -In case the array needs to be dynamically created (and therefore the array size -cannot be inferred by the compiler), you can give `ElementsAreArray()` an -additional argument to specify the array size: - -```cpp -using ::testing::ElementsAreArray; -... - int* const expected_vector3 = new int[count]; - ... fill expected_vector3 with values ... - EXPECT_CALL(mock, Foo(ElementsAreArray(expected_vector3, count))); -``` - -Use `Pair` when comparing maps or other associative containers. - -```cpp -using testing::ElementsAre; -using testing::Pair; -... - std::map<string, int> m = {{"a", 1}, {"b", 2}, {"c", 3}}; - EXPECT_THAT(m, ElementsAre(Pair("a", 1), Pair("b", 2), Pair("c", 3))); -``` - -**Tips:** - -* `ElementsAre*()` can be used to match *any* container that implements the - STL iterator pattern (i.e. it has a `const_iterator` type and supports - `begin()/end()`), not just the ones defined in STL. It will even work with - container types yet to be written - as long as they follows the above - pattern. -* You can use nested `ElementsAre*()` to match nested (multi-dimensional) - containers. -* If the container is passed by pointer instead of by reference, just write - `Pointee(ElementsAre*(...))`. -* The order of elements *matters* for `ElementsAre*()`. If you are using it - with containers whose element order are undefined (e.g. `hash_map`) you - should use `WhenSorted` around `ElementsAre`. - -### Sharing Matchers - -Under the hood, a gMock matcher object consists of a pointer to a ref-counted -implementation object. Copying matchers is allowed and very efficient, as only -the pointer is copied. When the last matcher that references the implementation -object dies, the implementation object will be deleted. - -Therefore, if you have some complex matcher that you want to use again and -again, there is no need to build it everytime. Just assign it to a matcher -variable and use that variable repeatedly! For example, - -```cpp -using ::testing::AllOf; -using ::testing::Gt; -using ::testing::Le; -using ::testing::Matcher; -... - Matcher<int> in_range = AllOf(Gt(5), Le(10)); - ... use in_range as a matcher in multiple EXPECT_CALLs ... -``` - -### Matchers must have no side-effects {#PureMatchers} - -WARNING: gMock does not guarantee when or how many times a matcher will be -invoked. Therefore, all matchers must be *purely functional*: they cannot have -any side effects, and the match result must not depend on anything other than -the matcher's parameters and the value being matched. - -This requirement must be satisfied no matter how a matcher is defined (e.g., if -it is one of the standard matchers, or a custom matcher). In particular, a -matcher can never call a mock function, as that will affect the state of the -mock object and gMock. - -## Setting Expectations - -### Knowing When to Expect {#UseOnCall} - -<!-- GOOGLETEST_CM0018 DO NOT DELETE --> - -**`ON_CALL`** is likely the *single most under-utilized construct* in gMock. - -There are basically two constructs for defining the behavior of a mock object: -`ON_CALL` and `EXPECT_CALL`. The difference? `ON_CALL` defines what happens when -a mock method is called, but <em>doesn't imply any expectation on the method -being called</em>. `EXPECT_CALL` not only defines the behavior, but also sets an -expectation that <em>the method will be called with the given arguments, for the -given number of times</em> (and *in the given order* when you specify the order -too). - -Since `EXPECT_CALL` does more, isn't it better than `ON_CALL`? Not really. Every -`EXPECT_CALL` adds a constraint on the behavior of the code under test. Having -more constraints than necessary is *baaad* - even worse than not having enough -constraints. - -This may be counter-intuitive. How could tests that verify more be worse than -tests that verify less? Isn't verification the whole point of tests? - -The answer lies in *what* a test should verify. **A good test verifies the -contract of the code.** If a test over-specifies, it doesn't leave enough -freedom to the implementation. As a result, changing the implementation without -breaking the contract (e.g. refactoring and optimization), which should be -perfectly fine to do, can break such tests. Then you have to spend time fixing -them, only to see them broken again the next time the implementation is changed. - -Keep in mind that one doesn't have to verify more than one property in one test. -In fact, **it's a good style to verify only one thing in one test.** If you do -that, a bug will likely break only one or two tests instead of dozens (which -case would you rather debug?). If you are also in the habit of giving tests -descriptive names that tell what they verify, you can often easily guess what's -wrong just from the test log itself. - -So use `ON_CALL` by default, and only use `EXPECT_CALL` when you actually intend -to verify that the call is made. For example, you may have a bunch of `ON_CALL`s -in your test fixture to set the common mock behavior shared by all tests in the -same group, and write (scarcely) different `EXPECT_CALL`s in different `TEST_F`s -to verify different aspects of the code's behavior. Compared with the style -where each `TEST` has many `EXPECT_CALL`s, this leads to tests that are more -resilient to implementational changes (and thus less likely to require -maintenance) and makes the intent of the tests more obvious (so they are easier -to maintain when you do need to maintain them). - -If you are bothered by the "Uninteresting mock function call" message printed -when a mock method without an `EXPECT_CALL` is called, you may use a `NiceMock` -instead to suppress all such messages for the mock object, or suppress the -message for specific methods by adding `EXPECT_CALL(...).Times(AnyNumber())`. DO -NOT suppress it by blindly adding an `EXPECT_CALL(...)`, or you'll have a test -that's a pain to maintain. - -### Ignoring Uninteresting Calls - -If you are not interested in how a mock method is called, just don't say -anything about it. In this case, if the method is ever called, gMock will -perform its default action to allow the test program to continue. If you are not -happy with the default action taken by gMock, you can override it using -`DefaultValue<T>::Set()` (described [here](#DefaultValue)) or `ON_CALL()`. - -Please note that once you expressed interest in a particular mock method (via -`EXPECT_CALL()`), all invocations to it must match some expectation. If this -function is called but the arguments don't match any `EXPECT_CALL()` statement, -it will be an error. - -### Disallowing Unexpected Calls - -If a mock method shouldn't be called at all, explicitly say so: - -```cpp -using ::testing::_; -... - EXPECT_CALL(foo, Bar(_)) - .Times(0); -``` - -If some calls to the method are allowed, but the rest are not, just list all the -expected calls: - -```cpp -using ::testing::AnyNumber; -using ::testing::Gt; -... - EXPECT_CALL(foo, Bar(5)); - EXPECT_CALL(foo, Bar(Gt(10))) - .Times(AnyNumber()); -``` - -A call to `foo.Bar()` that doesn't match any of the `EXPECT_CALL()` statements -will be an error. - -### Understanding Uninteresting vs Unexpected Calls {#uninteresting-vs-unexpected} - -*Uninteresting* calls and *unexpected* calls are different concepts in gMock. -*Very* different. - -A call `x.Y(...)` is **uninteresting** if there's *not even a single* -`EXPECT_CALL(x, Y(...))` set. In other words, the test isn't interested in the -`x.Y()` method at all, as evident in that the test doesn't care to say anything -about it. - -A call `x.Y(...)` is **unexpected** if there are *some* `EXPECT_CALL(x, -Y(...))`s set, but none of them matches the call. Put another way, the test is -interested in the `x.Y()` method (therefore it explicitly sets some -`EXPECT_CALL` to verify how it's called); however, the verification fails as the -test doesn't expect this particular call to happen. - -**An unexpected call is always an error,** as the code under test doesn't behave -the way the test expects it to behave. - -**By default, an uninteresting call is not an error,** as it violates no -constraint specified by the test. (gMock's philosophy is that saying nothing -means there is no constraint.) However, it leads to a warning, as it *might* -indicate a problem (e.g. the test author might have forgotten to specify a -constraint). - -In gMock, `NiceMock` and `StrictMock` can be used to make a mock class "nice" or -"strict". How does this affect uninteresting calls and unexpected calls? - -A **nice mock** suppresses uninteresting call *warnings*. It is less chatty than -the default mock, but otherwise is the same. If a test fails with a default -mock, it will also fail using a nice mock instead. And vice versa. Don't expect -making a mock nice to change the test's result. - -A **strict mock** turns uninteresting call warnings into errors. So making a -mock strict may change the test's result. - -Let's look at an example: - -```cpp -TEST(...) { - NiceMock<MockDomainRegistry> mock_registry; - EXPECT_CALL(mock_registry, GetDomainOwner("google.com")) - .WillRepeatedly(Return("Larry Page")); - - // Use mock_registry in code under test. - ... &mock_registry ... -} -``` - -The sole `EXPECT_CALL` here says that all calls to `GetDomainOwner()` must have -`"google.com"` as the argument. If `GetDomainOwner("yahoo.com")` is called, it -will be an unexpected call, and thus an error. *Having a nice mock doesn't -change the severity of an unexpected call.* - -So how do we tell gMock that `GetDomainOwner()` can be called with some other -arguments as well? The standard technique is to add a "catch all" `EXPECT_CALL`: - -```cpp - EXPECT_CALL(mock_registry, GetDomainOwner(_)) - .Times(AnyNumber()); // catches all other calls to this method. - EXPECT_CALL(mock_registry, GetDomainOwner("google.com")) - .WillRepeatedly(Return("Larry Page")); -``` - -Remember that `_` is the wildcard matcher that matches anything. With this, if -`GetDomainOwner("google.com")` is called, it will do what the second -`EXPECT_CALL` says; if it is called with a different argument, it will do what -the first `EXPECT_CALL` says. - -Note that the order of the two `EXPECT_CALL`s is important, as a newer -`EXPECT_CALL` takes precedence over an older one. - -For more on uninteresting calls, nice mocks, and strict mocks, read -["The Nice, the Strict, and the Naggy"](#NiceStrictNaggy). - -### Ignoring Uninteresting Arguments {#ParameterlessExpectations} - -If your test doesn't care about the parameters (it only cares about the number -or order of calls), you can often simply omit the parameter list: - -```cpp - // Expect foo.Bar( ... ) twice with any arguments. - EXPECT_CALL(foo, Bar).Times(2); - - // Delegate to the given method whenever the factory is invoked. - ON_CALL(foo_factory, MakeFoo) - .WillByDefault(&BuildFooForTest); -``` - -This functionality is only available when a method is not overloaded; to prevent -unexpected behavior it is a compilation error to try to set an expectation on a -method where the specific overload is ambiguous. You can work around this by -supplying a [simpler mock interface](#SimplerInterfaces) than the mocked class -provides. - -This pattern is also useful when the arguments are interesting, but match logic -is substantially complex. You can leave the argument list unspecified and use -SaveArg actions to [save the values for later verification](#SaveArgVerify). If -you do that, you can easily differentiate calling the method the wrong number of -times from calling it with the wrong arguments. - -### Expecting Ordered Calls {#OrderedCalls} - -Although an `EXPECT_CALL()` statement defined later takes precedence when gMock -tries to match a function call with an expectation, by default calls don't have -to happen in the order `EXPECT_CALL()` statements are written. For example, if -the arguments match the matchers in the second `EXPECT_CALL()`, but not those in -the first and third, then the second expectation will be used. - -If you would rather have all calls occur in the order of the expectations, put -the `EXPECT_CALL()` statements in a block where you define a variable of type -`InSequence`: - -```cpp -using ::testing::_; -using ::testing::InSequence; - - { - InSequence s; - - EXPECT_CALL(foo, DoThis(5)); - EXPECT_CALL(bar, DoThat(_)) - .Times(2); - EXPECT_CALL(foo, DoThis(6)); - } -``` - -In this example, we expect a call to `foo.DoThis(5)`, followed by two calls to -`bar.DoThat()` where the argument can be anything, which are in turn followed by -a call to `foo.DoThis(6)`. If a call occurred out-of-order, gMock will report an -error. - -### Expecting Partially Ordered Calls {#PartialOrder} - -Sometimes requiring everything to occur in a predetermined order can lead to -brittle tests. For example, we may care about `A` occurring before both `B` and -`C`, but aren't interested in the relative order of `B` and `C`. In this case, -the test should reflect our real intent, instead of being overly constraining. - -gMock allows you to impose an arbitrary DAG (directed acyclic graph) on the -calls. One way to express the DAG is to use the -[After](cheat_sheet.md#AfterClause) clause of `EXPECT_CALL`. - -Another way is via the `InSequence()` clause (not the same as the `InSequence` -class), which we borrowed from jMock 2. It's less flexible than `After()`, but -more convenient when you have long chains of sequential calls, as it doesn't -require you to come up with different names for the expectations in the chains. -Here's how it works: - -If we view `EXPECT_CALL()` statements as nodes in a graph, and add an edge from -node A to node B wherever A must occur before B, we can get a DAG. We use the -term "sequence" to mean a directed path in this DAG. Now, if we decompose the -DAG into sequences, we just need to know which sequences each `EXPECT_CALL()` -belongs to in order to be able to reconstruct the original DAG. - -So, to specify the partial order on the expectations we need to do two things: -first to define some `Sequence` objects, and then for each `EXPECT_CALL()` say -which `Sequence` objects it is part of. - -Expectations in the same sequence must occur in the order they are written. For -example, - -```cpp -using ::testing::Sequence; -... - Sequence s1, s2; - - EXPECT_CALL(foo, A()) - .InSequence(s1, s2); - EXPECT_CALL(bar, B()) - .InSequence(s1); - EXPECT_CALL(bar, C()) - .InSequence(s2); - EXPECT_CALL(foo, D()) - .InSequence(s2); -``` - -specifies the following DAG (where `s1` is `A -> B`, and `s2` is `A -> C -> D`): - -```text - +---> B - | - A ---| - | - +---> C ---> D -``` - -This means that A must occur before B and C, and C must occur before D. There's -no restriction about the order other than these. - -### Controlling When an Expectation Retires - -When a mock method is called, gMock only considers expectations that are still -active. An expectation is active when created, and becomes inactive (aka -*retires*) when a call that has to occur later has occurred. For example, in - -```cpp -using ::testing::_; -using ::testing::Sequence; -... - Sequence s1, s2; - - EXPECT_CALL(log, Log(WARNING, _, "File too large.")) // #1 - .Times(AnyNumber()) - .InSequence(s1, s2); - EXPECT_CALL(log, Log(WARNING, _, "Data set is empty.")) // #2 - .InSequence(s1); - EXPECT_CALL(log, Log(WARNING, _, "User not found.")) // #3 - .InSequence(s2); -``` - -as soon as either #2 or #3 is matched, #1 will retire. If a warning `"File too -large."` is logged after this, it will be an error. - -Note that an expectation doesn't retire automatically when it's saturated. For -example, - -```cpp -using ::testing::_; -... - EXPECT_CALL(log, Log(WARNING, _, _)); // #1 - EXPECT_CALL(log, Log(WARNING, _, "File too large.")); // #2 -``` - -says that there will be exactly one warning with the message `"File too -large."`. If the second warning contains this message too, #2 will match again -and result in an upper-bound-violated error. - -If this is not what you want, you can ask an expectation to retire as soon as it -becomes saturated: - -```cpp -using ::testing::_; -... - EXPECT_CALL(log, Log(WARNING, _, _)); // #1 - EXPECT_CALL(log, Log(WARNING, _, "File too large.")) // #2 - .RetiresOnSaturation(); -``` - -Here #2 can be used only once, so if you have two warnings with the message -`"File too large."`, the first will match #2 and the second will match #1 - -there will be no error. - -## Using Actions - -### Returning References from Mock Methods - -If a mock function's return type is a reference, you need to use `ReturnRef()` -instead of `Return()` to return a result: - -```cpp -using ::testing::ReturnRef; - -class MockFoo : public Foo { - public: - MOCK_METHOD(Bar&, GetBar, (), (override)); -}; -... - MockFoo foo; - Bar bar; - EXPECT_CALL(foo, GetBar()) - .WillOnce(ReturnRef(bar)); -... -``` - -### Returning Live Values from Mock Methods - -The `Return(x)` action saves a copy of `x` when the action is created, and -always returns the same value whenever it's executed. Sometimes you may want to -instead return the *live* value of `x` (i.e. its value at the time when the -action is *executed*.). Use either `ReturnRef()` or `ReturnPointee()` for this -purpose. - -If the mock function's return type is a reference, you can do it using -`ReturnRef(x)`, as shown in the previous recipe ("Returning References from Mock -Methods"). However, gMock doesn't let you use `ReturnRef()` in a mock function -whose return type is not a reference, as doing that usually indicates a user -error. So, what shall you do? - -Though you may be tempted, DO NOT use `std::ref()`: - -```cpp -using testing::Return; - -class MockFoo : public Foo { - public: - MOCK_METHOD(int, GetValue, (), (override)); -}; -... - int x = 0; - MockFoo foo; - EXPECT_CALL(foo, GetValue()) - .WillRepeatedly(Return(std::ref(x))); // Wrong! - x = 42; - EXPECT_EQ(42, foo.GetValue()); -``` - -Unfortunately, it doesn't work here. The above code will fail with error: - -```text -Value of: foo.GetValue() - Actual: 0 -Expected: 42 -``` - -The reason is that `Return(*value*)` converts `value` to the actual return type -of the mock function at the time when the action is *created*, not when it is -*executed*. (This behavior was chosen for the action to be safe when `value` is -a proxy object that references some temporary objects.) As a result, -`std::ref(x)` is converted to an `int` value (instead of a `const int&`) when -the expectation is set, and `Return(std::ref(x))` will always return 0. - -`ReturnPointee(pointer)` was provided to solve this problem specifically. It -returns the value pointed to by `pointer` at the time the action is *executed*: - -```cpp -using testing::ReturnPointee; -... - int x = 0; - MockFoo foo; - EXPECT_CALL(foo, GetValue()) - .WillRepeatedly(ReturnPointee(&x)); // Note the & here. - x = 42; - EXPECT_EQ(42, foo.GetValue()); // This will succeed now. -``` - -### Combining Actions - -Want to do more than one thing when a function is called? That's fine. `DoAll()` -allow you to do sequence of actions every time. Only the return value of the -last action in the sequence will be used. - -```cpp -using ::testing::_; -using ::testing::DoAll; - -class MockFoo : public Foo { - public: - MOCK_METHOD(bool, Bar, (int n), (override)); -}; -... - EXPECT_CALL(foo, Bar(_)) - .WillOnce(DoAll(action_1, - action_2, - ... - action_n)); -``` - -### Verifying Complex Arguments {#SaveArgVerify} - -If you want to verify that a method is called with a particular argument but the -match criteria is complex, it can be difficult to distinguish between -cardinality failures (calling the method the wrong number of times) and argument -match failures. Similarly, if you are matching multiple parameters, it may not -be easy to distinguishing which argument failed to match. For example: - -```cpp - // Not ideal: this could fail because of a problem with arg1 or arg2, or maybe - // just the method wasn't called. - EXPECT_CALL(foo, SendValues(_, ElementsAre(1, 4, 4, 7), EqualsProto( ... ))); -``` - -You can instead save the arguments and test them individually: - -```cpp - EXPECT_CALL(foo, SendValues) - .WillOnce(DoAll(SaveArg<1>(&actual_array), SaveArg<2>(&actual_proto))); - ... run the test - EXPECT_THAT(actual_array, ElementsAre(1, 4, 4, 7)); - EXPECT_THAT(actual_proto, EqualsProto( ... )); -``` - -### Mocking Side Effects {#MockingSideEffects} - -Sometimes a method exhibits its effect not via returning a value but via side -effects. For example, it may change some global state or modify an output -argument. To mock side effects, in general you can define your own action by -implementing `::testing::ActionInterface`. - -If all you need to do is to change an output argument, the built-in -`SetArgPointee()` action is convenient: - -```cpp -using ::testing::_; -using ::testing::SetArgPointee; - -class MockMutator : public Mutator { - public: - MOCK_METHOD(void, Mutate, (bool mutate, int* value), (override)); - ... -} -... - MockMutator mutator; - EXPECT_CALL(mutator, Mutate(true, _)) - .WillOnce(SetArgPointee<1>(5)); -``` - -In this example, when `mutator.Mutate()` is called, we will assign 5 to the -`int` variable pointed to by argument #1 (0-based). - -`SetArgPointee()` conveniently makes an internal copy of the value you pass to -it, removing the need to keep the value in scope and alive. The implication -however is that the value must have a copy constructor and assignment operator. - -If the mock method also needs to return a value as well, you can chain -`SetArgPointee()` with `Return()` using `DoAll()`, remembering to put the -`Return()` statement last: - -```cpp -using ::testing::_; -using ::testing::Return; -using ::testing::SetArgPointee; - -class MockMutator : public Mutator { - public: - ... - MOCK_METHOD(bool, MutateInt, (int* value), (override)); -} -... - MockMutator mutator; - EXPECT_CALL(mutator, MutateInt(_)) - .WillOnce(DoAll(SetArgPointee<0>(5), - Return(true))); -``` - -Note, however, that if you use the `ReturnOKWith()` method, it will override the -values provided by `SetArgPointee()` in the response parameters of your function -call. - -If the output argument is an array, use the `SetArrayArgument<N>(first, last)` -action instead. It copies the elements in source range `[first, last)` to the -array pointed to by the `N`-th (0-based) argument: - -```cpp -using ::testing::NotNull; -using ::testing::SetArrayArgument; - -class MockArrayMutator : public ArrayMutator { - public: - MOCK_METHOD(void, Mutate, (int* values, int num_values), (override)); - ... -} -... - MockArrayMutator mutator; - int values[5] = {1, 2, 3, 4, 5}; - EXPECT_CALL(mutator, Mutate(NotNull(), 5)) - .WillOnce(SetArrayArgument<0>(values, values + 5)); -``` - -This also works when the argument is an output iterator: - -```cpp -using ::testing::_; -using ::testing::SetArrayArgument; - -class MockRolodex : public Rolodex { - public: - MOCK_METHOD(void, GetNames, (std::back_insert_iterator<vector<string>>), - (override)); - ... -} -... - MockRolodex rolodex; - vector<string> names; - names.push_back("George"); - names.push_back("John"); - names.push_back("Thomas"); - EXPECT_CALL(rolodex, GetNames(_)) - .WillOnce(SetArrayArgument<0>(names.begin(), names.end())); -``` - -### Changing a Mock Object's Behavior Based on the State - -If you expect a call to change the behavior of a mock object, you can use -`::testing::InSequence` to specify different behaviors before and after the -call: - -```cpp -using ::testing::InSequence; -using ::testing::Return; - -... - { - InSequence seq; - EXPECT_CALL(my_mock, IsDirty()) - .WillRepeatedly(Return(true)); - EXPECT_CALL(my_mock, Flush()); - EXPECT_CALL(my_mock, IsDirty()) - .WillRepeatedly(Return(false)); - } - my_mock.FlushIfDirty(); -``` - -This makes `my_mock.IsDirty()` return `true` before `my_mock.Flush()` is called -and return `false` afterwards. - -If the behavior change is more complex, you can store the effects in a variable -and make a mock method get its return value from that variable: - -```cpp -using ::testing::_; -using ::testing::SaveArg; -using ::testing::Return; - -ACTION_P(ReturnPointee, p) { return *p; } -... - int previous_value = 0; - EXPECT_CALL(my_mock, GetPrevValue) - .WillRepeatedly(ReturnPointee(&previous_value)); - EXPECT_CALL(my_mock, UpdateValue) - .WillRepeatedly(SaveArg<0>(&previous_value)); - my_mock.DoSomethingToUpdateValue(); -``` - -Here `my_mock.GetPrevValue()` will always return the argument of the last -`UpdateValue()` call. - -### Setting the Default Value for a Return Type {#DefaultValue} - -If a mock method's return type is a built-in C++ type or pointer, by default it -will return 0 when invoked. Also, in C++ 11 and above, a mock method whose -return type has a default constructor will return a default-constructed value by -default. You only need to specify an action if this default value doesn't work -for you. - -Sometimes, you may want to change this default value, or you may want to specify -a default value for types gMock doesn't know about. You can do this using the -`::testing::DefaultValue` class template: - -```cpp -using ::testing::DefaultValue; - -class MockFoo : public Foo { - public: - MOCK_METHOD(Bar, CalculateBar, (), (override)); -}; - - -... - Bar default_bar; - // Sets the default return value for type Bar. - DefaultValue<Bar>::Set(default_bar); - - MockFoo foo; - - // We don't need to specify an action here, as the default - // return value works for us. - EXPECT_CALL(foo, CalculateBar()); - - foo.CalculateBar(); // This should return default_bar. - - // Unsets the default return value. - DefaultValue<Bar>::Clear(); -``` - -Please note that changing the default value for a type can make your tests hard -to understand. We recommend you to use this feature judiciously. For example, -you may want to make sure the `Set()` and `Clear()` calls are right next to the -code that uses your mock. - -### Setting the Default Actions for a Mock Method - -You've learned how to change the default value of a given type. However, this -may be too coarse for your purpose: perhaps you have two mock methods with the -same return type and you want them to have different behaviors. The `ON_CALL()` -macro allows you to customize your mock's behavior at the method level: - -```cpp -using ::testing::_; -using ::testing::AnyNumber; -using ::testing::Gt; -using ::testing::Return; -... - ON_CALL(foo, Sign(_)) - .WillByDefault(Return(-1)); - ON_CALL(foo, Sign(0)) - .WillByDefault(Return(0)); - ON_CALL(foo, Sign(Gt(0))) - .WillByDefault(Return(1)); - - EXPECT_CALL(foo, Sign(_)) - .Times(AnyNumber()); - - foo.Sign(5); // This should return 1. - foo.Sign(-9); // This should return -1. - foo.Sign(0); // This should return 0. -``` - -As you may have guessed, when there are more than one `ON_CALL()` statements, -the newer ones in the order take precedence over the older ones. In other words, -the **last** one that matches the function arguments will be used. This matching -order allows you to set up the common behavior in a mock object's constructor or -the test fixture's set-up phase and specialize the mock's behavior later. - -Note that both `ON_CALL` and `EXPECT_CALL` have the same "later statements take -precedence" rule, but they don't interact. That is, `EXPECT_CALL`s have their -own precedence order distinct from the `ON_CALL` precedence order. - -### Using Functions/Methods/Functors/Lambdas as Actions {#FunctionsAsActions} - -If the built-in actions don't suit you, you can use an existing callable -(function, `std::function`, method, functor, lambda) as an action. - -<!-- GOOGLETEST_CM0024 DO NOT DELETE --> - -```cpp -using ::testing::_; using ::testing::Invoke; - -class MockFoo : public Foo { - public: - MOCK_METHOD(int, Sum, (int x, int y), (override)); - MOCK_METHOD(bool, ComplexJob, (int x), (override)); -}; - -int CalculateSum(int x, int y) { return x + y; } -int Sum3(int x, int y, int z) { return x + y + z; } - -class Helper { - public: - bool ComplexJob(int x); -}; - -... - MockFoo foo; - Helper helper; - EXPECT_CALL(foo, Sum(_, _)) - .WillOnce(&CalculateSum) - .WillRepeatedly(Invoke(NewPermanentCallback(Sum3, 1))); - EXPECT_CALL(foo, ComplexJob(_)) - .WillOnce(Invoke(&helper, &Helper::ComplexJob)) - .WillOnce([] { return true; }) - .WillRepeatedly([](int x) { return x > 0; }); - - foo.Sum(5, 6); // Invokes CalculateSum(5, 6). - foo.Sum(2, 3); // Invokes Sum3(1, 2, 3). - foo.ComplexJob(10); // Invokes helper.ComplexJob(10). - foo.ComplexJob(-1); // Invokes the inline lambda. -``` - -The only requirement is that the type of the function, etc must be *compatible* -with the signature of the mock function, meaning that the latter's arguments (if -it takes any) can be implicitly converted to the corresponding arguments of the -former, and the former's return type can be implicitly converted to that of the -latter. So, you can invoke something whose type is *not* exactly the same as the -mock function, as long as it's safe to do so - nice, huh? - -**`Note:`{.escaped}** - -* The action takes ownership of the callback and will delete it when the - action itself is destructed. -* If the type of a callback is derived from a base callback type `C`, you need - to implicitly cast it to `C` to resolve the overloading, e.g. - - ```cpp - using ::testing::Invoke; - ... - ResultCallback<bool>* is_ok = ...; - ... Invoke(is_ok) ...; // This works. - - BlockingClosure* done = new BlockingClosure; - ... Invoke(implicit_cast<Closure*>(done)) ...; // The cast is necessary. - ``` - -### Using Functions with Extra Info as Actions - -The function or functor you call using `Invoke()` must have the same number of -arguments as the mock function you use it for. Sometimes you may have a function -that takes more arguments, and you are willing to pass in the extra arguments -yourself to fill the gap. You can do this in gMock using callbacks with -pre-bound arguments. Here's an example: - -```cpp -using ::testing::Invoke; - -class MockFoo : public Foo { - public: - MOCK_METHOD(char, DoThis, (int n), (override)); -}; - -char SignOfSum(int x, int y) { - const int sum = x + y; - return (sum > 0) ? '+' : (sum < 0) ? '-' : '0'; -} - -TEST_F(FooTest, Test) { - MockFoo foo; - - EXPECT_CALL(foo, DoThis(2)) - .WillOnce(Invoke(NewPermanentCallback(SignOfSum, 5))); - EXPECT_EQ('+', foo.DoThis(2)); // Invokes SignOfSum(5, 2). -} -``` - -### Invoking a Function/Method/Functor/Lambda/Callback Without Arguments - -`Invoke()` passes the mock function's arguments to the function, etc being -invoked such that the callee has the full context of the call to work with. If -the invoked function is not interested in some or all of the arguments, it can -simply ignore them. - -Yet, a common pattern is that a test author wants to invoke a function without -the arguments of the mock function. She could do that using a wrapper function -that throws away the arguments before invoking an underlining nullary function. -Needless to say, this can be tedious and obscures the intent of the test. - -There are two solutions to this problem. First, you can pass any callable of -zero args as an action. Alternatively, use `InvokeWithoutArgs()`, which is like -`Invoke()` except that it doesn't pass the mock function's arguments to the -callee. Here's an example of each: - -```cpp -using ::testing::_; -using ::testing::InvokeWithoutArgs; - -class MockFoo : public Foo { - public: - MOCK_METHOD(bool, ComplexJob, (int n), (override)); -}; - -bool Job1() { ... } -bool Job2(int n, char c) { ... } - -... - MockFoo foo; - EXPECT_CALL(foo, ComplexJob(_)) - .WillOnce([] { Job1(); }); - .WillOnce(InvokeWithoutArgs(NewPermanentCallback(Job2, 5, 'a'))); - - foo.ComplexJob(10); // Invokes Job1(). - foo.ComplexJob(20); // Invokes Job2(5, 'a'). -``` - -**`Note:`{.escaped}** - -* The action takes ownership of the callback and will delete it when the - action itself is destructed. -* If the type of a callback is derived from a base callback type `C`, you need - to implicitly cast it to `C` to resolve the overloading, e.g. - - ```cpp - using ::testing::InvokeWithoutArgs; - ... - ResultCallback<bool>* is_ok = ...; - ... InvokeWithoutArgs(is_ok) ...; // This works. - - BlockingClosure* done = ...; - ... InvokeWithoutArgs(implicit_cast<Closure*>(done)) ...; - // The cast is necessary. - ``` - -### Invoking an Argument of the Mock Function - -Sometimes a mock function will receive a function pointer, a functor (in other -words, a "callable") as an argument, e.g. - -```cpp -class MockFoo : public Foo { - public: - MOCK_METHOD(bool, DoThis, (int n, (ResultCallback1<bool, int>* callback)), - (override)); -}; -``` - -and you may want to invoke this callable argument: - -```cpp -using ::testing::_; -... - MockFoo foo; - EXPECT_CALL(foo, DoThis(_, _)) - .WillOnce(...); - // Will execute callback->Run(5), where callback is the - // second argument DoThis() receives. -``` - -NOTE: The section below is legacy documentation from before C++ had lambdas: - -Arghh, you need to refer to a mock function argument but C++ has no lambda -(yet), so you have to define your own action. :-( Or do you really? - -Well, gMock has an action to solve *exactly* this problem: - -```cpp -InvokeArgument<N>(arg_1, arg_2, ..., arg_m) -``` - -will invoke the `N`-th (0-based) argument the mock function receives, with -`arg_1`, `arg_2`, ..., and `arg_m`. No matter if the argument is a function -pointer, a functor, or a callback. gMock handles them all. - -With that, you could write: - -```cpp -using ::testing::_; -using ::testing::InvokeArgument; -... - EXPECT_CALL(foo, DoThis(_, _)) - .WillOnce(InvokeArgument<1>(5)); - // Will execute callback->Run(5), where callback is the - // second argument DoThis() receives. -``` - -What if the callable takes an argument by reference? No problem - just wrap it -inside `std::ref()`: - -```cpp - ... - MOCK_METHOD(bool, Bar, - ((ResultCallback2<bool, int, const Helper&>* callback)), - (override)); - ... - using ::testing::_; - using ::testing::InvokeArgument; - ... - MockFoo foo; - Helper helper; - ... - EXPECT_CALL(foo, Bar(_)) - .WillOnce(InvokeArgument<0>(5, std::ref(helper))); - // std::ref(helper) guarantees that a reference to helper, not a copy of - // it, will be passed to the callback. -``` - -What if the callable takes an argument by reference and we do **not** wrap the -argument in `std::ref()`? Then `InvokeArgument()` will *make a copy* of the -argument, and pass a *reference to the copy*, instead of a reference to the -original value, to the callable. This is especially handy when the argument is a -temporary value: - -```cpp - ... - MOCK_METHOD(bool, DoThat, (bool (*f)(const double& x, const string& s)), - (override)); - ... - using ::testing::_; - using ::testing::InvokeArgument; - ... - MockFoo foo; - ... - EXPECT_CALL(foo, DoThat(_)) - .WillOnce(InvokeArgument<0>(5.0, string("Hi"))); - // Will execute (*f)(5.0, string("Hi")), where f is the function pointer - // DoThat() receives. Note that the values 5.0 and string("Hi") are - // temporary and dead once the EXPECT_CALL() statement finishes. Yet - // it's fine to perform this action later, since a copy of the values - // are kept inside the InvokeArgument action. -``` - -### Ignoring an Action's Result - -Sometimes you have an action that returns *something*, but you need an action -that returns `void` (perhaps you want to use it in a mock function that returns -`void`, or perhaps it needs to be used in `DoAll()` and it's not the last in the -list). `IgnoreResult()` lets you do that. For example: - -```cpp -using ::testing::_; -using ::testing::DoAll; -using ::testing::IgnoreResult; -using ::testing::Return; - -int Process(const MyData& data); -string DoSomething(); - -class MockFoo : public Foo { - public: - MOCK_METHOD(void, Abc, (const MyData& data), (override)); - MOCK_METHOD(bool, Xyz, (), (override)); -}; - - ... - MockFoo foo; - EXPECT_CALL(foo, Abc(_)) - // .WillOnce(Invoke(Process)); - // The above line won't compile as Process() returns int but Abc() needs - // to return void. - .WillOnce(IgnoreResult(Process)); - EXPECT_CALL(foo, Xyz()) - .WillOnce(DoAll(IgnoreResult(DoSomething), - // Ignores the string DoSomething() returns. - Return(true))); -``` - -Note that you **cannot** use `IgnoreResult()` on an action that already returns -`void`. Doing so will lead to ugly compiler errors. - -### Selecting an Action's Arguments {#SelectingArgs} - -Say you have a mock function `Foo()` that takes seven arguments, and you have a -custom action that you want to invoke when `Foo()` is called. Trouble is, the -custom action only wants three arguments: - -```cpp -using ::testing::_; -using ::testing::Invoke; -... - MOCK_METHOD(bool, Foo, - (bool visible, const string& name, int x, int y, - (const map<pair<int, int>>), double& weight, double min_weight, - double max_wight)); -... -bool IsVisibleInQuadrant1(bool visible, int x, int y) { - return visible && x >= 0 && y >= 0; -} -... - EXPECT_CALL(mock, Foo) - .WillOnce(Invoke(IsVisibleInQuadrant1)); // Uh, won't compile. :-( -``` - -To please the compiler God, you need to define an "adaptor" that has the same -signature as `Foo()` and calls the custom action with the right arguments: - -```cpp -using ::testing::_; -using ::testing::Invoke; -... -bool MyIsVisibleInQuadrant1(bool visible, const string& name, int x, int y, - const map<pair<int, int>, double>& weight, - double min_weight, double max_wight) { - return IsVisibleInQuadrant1(visible, x, y); -} -... - EXPECT_CALL(mock, Foo) - .WillOnce(Invoke(MyIsVisibleInQuadrant1)); // Now it works. -``` - -But isn't this awkward? - -gMock provides a generic *action adaptor*, so you can spend your time minding -more important business than writing your own adaptors. Here's the syntax: - -```cpp -WithArgs<N1, N2, ..., Nk>(action) -``` - -creates an action that passes the arguments of the mock function at the given -indices (0-based) to the inner `action` and performs it. Using `WithArgs`, our -original example can be written as: - -```cpp -using ::testing::_; -using ::testing::Invoke; -using ::testing::WithArgs; -... - EXPECT_CALL(mock, Foo) - .WillOnce(WithArgs<0, 2, 3>(Invoke(IsVisibleInQuadrant1))); // No need to define your own adaptor. -``` - -For better readability, gMock also gives you: - -* `WithoutArgs(action)` when the inner `action` takes *no* argument, and -* `WithArg<N>(action)` (no `s` after `Arg`) when the inner `action` takes - *one* argument. - -As you may have realized, `InvokeWithoutArgs(...)` is just syntactic sugar for -`WithoutArgs(Invoke(...))`. - -Here are more tips: - -* The inner action used in `WithArgs` and friends does not have to be - `Invoke()` -- it can be anything. -* You can repeat an argument in the argument list if necessary, e.g. - `WithArgs<2, 3, 3, 5>(...)`. -* You can change the order of the arguments, e.g. `WithArgs<3, 2, 1>(...)`. -* The types of the selected arguments do *not* have to match the signature of - the inner action exactly. It works as long as they can be implicitly - converted to the corresponding arguments of the inner action. For example, - if the 4-th argument of the mock function is an `int` and `my_action` takes - a `double`, `WithArg<4>(my_action)` will work. - -### Ignoring Arguments in Action Functions - -The [selecting-an-action's-arguments](#SelectingArgs) recipe showed us one way -to make a mock function and an action with incompatible argument lists fit -together. The downside is that wrapping the action in `WithArgs<...>()` can get -tedious for people writing the tests. - -If you are defining a function (or method, functor, lambda, callback) to be used -with `Invoke*()`, and you are not interested in some of its arguments, an -alternative to `WithArgs` is to declare the uninteresting arguments as `Unused`. -This makes the definition less cluttered and less fragile in case the types of -the uninteresting arguments change. It could also increase the chance the action -function can be reused. For example, given - -```cpp - public: - MOCK_METHOD(double, Foo, double(const string& label, double x, double y), - (override)); - MOCK_METHOD(double, Bar, (int index, double x, double y), (override)); -``` - -instead of - -```cpp -using ::testing::_; -using ::testing::Invoke; - -double DistanceToOriginWithLabel(const string& label, double x, double y) { - return sqrt(x*x + y*y); -} -double DistanceToOriginWithIndex(int index, double x, double y) { - return sqrt(x*x + y*y); -} -... - EXPECT_CALL(mock, Foo("abc", _, _)) - .WillOnce(Invoke(DistanceToOriginWithLabel)); - EXPECT_CALL(mock, Bar(5, _, _)) - .WillOnce(Invoke(DistanceToOriginWithIndex)); -``` - -you could write - -```cpp -using ::testing::_; -using ::testing::Invoke; -using ::testing::Unused; - -double DistanceToOrigin(Unused, double x, double y) { - return sqrt(x*x + y*y); -} -... - EXPECT_CALL(mock, Foo("abc", _, _)) - .WillOnce(Invoke(DistanceToOrigin)); - EXPECT_CALL(mock, Bar(5, _, _)) - .WillOnce(Invoke(DistanceToOrigin)); -``` - -### Sharing Actions - -Just like matchers, a gMock action object consists of a pointer to a ref-counted -implementation object. Therefore copying actions is also allowed and very -efficient. When the last action that references the implementation object dies, -the implementation object will be deleted. - -If you have some complex action that you want to use again and again, you may -not have to build it from scratch everytime. If the action doesn't have an -internal state (i.e. if it always does the same thing no matter how many times -it has been called), you can assign it to an action variable and use that -variable repeatedly. For example: - -```cpp -using ::testing::Action; -using ::testing::DoAll; -using ::testing::Return; -using ::testing::SetArgPointee; -... - Action<bool(int*)> set_flag = DoAll(SetArgPointee<0>(5), - Return(true)); - ... use set_flag in .WillOnce() and .WillRepeatedly() ... -``` - -However, if the action has its own state, you may be surprised if you share the -action object. Suppose you have an action factory `IncrementCounter(init)` which -creates an action that increments and returns a counter whose initial value is -`init`, using two actions created from the same expression and using a shared -action will exhibit different behaviors. Example: - -```cpp - EXPECT_CALL(foo, DoThis()) - .WillRepeatedly(IncrementCounter(0)); - EXPECT_CALL(foo, DoThat()) - .WillRepeatedly(IncrementCounter(0)); - foo.DoThis(); // Returns 1. - foo.DoThis(); // Returns 2. - foo.DoThat(); // Returns 1 - Blah() uses a different - // counter than Bar()'s. -``` - -versus - -```cpp -using ::testing::Action; -... - Action<int()> increment = IncrementCounter(0); - EXPECT_CALL(foo, DoThis()) - .WillRepeatedly(increment); - EXPECT_CALL(foo, DoThat()) - .WillRepeatedly(increment); - foo.DoThis(); // Returns 1. - foo.DoThis(); // Returns 2. - foo.DoThat(); // Returns 3 - the counter is shared. -``` - -### Testing Asynchronous Behavior - -One oft-encountered problem with gMock is that it can be hard to test -asynchronous behavior. Suppose you had a `EventQueue` class that you wanted to -test, and you created a separate `EventDispatcher` interface so that you could -easily mock it out. However, the implementation of the class fired all the -events on a background thread, which made test timings difficult. You could just -insert `sleep()` statements and hope for the best, but that makes your test -behavior nondeterministic. A better way is to use gMock actions and -`Notification` objects to force your asynchronous test to behave synchronously. - -```cpp -using ::testing::DoAll; -using ::testing::InvokeWithoutArgs; -using ::testing::Return; - -class MockEventDispatcher : public EventDispatcher { - MOCK_METHOD(bool, DispatchEvent, (int32), (override)); -}; - -ACTION_P(Notify, notification) { - notification->Notify(); -} - -TEST(EventQueueTest, EnqueueEventTest) { - MockEventDispatcher mock_event_dispatcher; - EventQueue event_queue(&mock_event_dispatcher); - - const int32 kEventId = 321; - absl::Notification done; - EXPECT_CALL(mock_event_dispatcher, DispatchEvent(kEventId)) - .WillOnce(Notify(&done)); - - event_queue.EnqueueEvent(kEventId); - done.WaitForNotification(); -} -``` - -In the example above, we set our normal gMock expectations, but then add an -additional action to notify the `Notification` object. Now we can just call -`Notification::WaitForNotification()` in the main thread to wait for the -asynchronous call to finish. After that, our test suite is complete and we can -safely exit. - -Note: this example has a downside: namely, if the expectation is not satisfied, -our test will run forever. It will eventually time-out and fail, but it will -take longer and be slightly harder to debug. To alleviate this problem, you can -use `WaitForNotificationWithTimeout(ms)` instead of `WaitForNotification()`. - -## Misc Recipes on Using gMock - -### Mocking Methods That Use Move-Only Types - -C++11 introduced *move-only types*. A move-only-typed value can be moved from -one object to another, but cannot be copied. `std::unique_ptr<T>` is probably -the most commonly used move-only type. - -Mocking a method that takes and/or returns move-only types presents some -challenges, but nothing insurmountable. This recipe shows you how you can do it. -Note that the support for move-only method arguments was only introduced to -gMock in April 2017; in older code, you may find more complex -[workarounds](#LegacyMoveOnly) for lack of this feature. - -Let’s say we are working on a fictional project that lets one post and share -snippets called “buzzes”. Your code uses these types: - -```cpp -enum class AccessLevel { kInternal, kPublic }; - -class Buzz { - public: - explicit Buzz(AccessLevel access) { ... } - ... -}; - -class Buzzer { - public: - virtual ~Buzzer() {} - virtual std::unique_ptr<Buzz> MakeBuzz(StringPiece text) = 0; - virtual bool ShareBuzz(std::unique_ptr<Buzz> buzz, int64_t timestamp) = 0; - ... -}; -``` - -A `Buzz` object represents a snippet being posted. A class that implements the -`Buzzer` interface is capable of creating and sharing `Buzz`es. Methods in -`Buzzer` may return a `unique_ptr<Buzz>` or take a `unique_ptr<Buzz>`. Now we -need to mock `Buzzer` in our tests. - -To mock a method that accepts or returns move-only types, you just use the -familiar `MOCK_METHOD` syntax as usual: - -```cpp -class MockBuzzer : public Buzzer { - public: - MOCK_METHOD(std::unique_ptr<Buzz>, MakeBuzz, (StringPiece text), (override)); - MOCK_METHOD(bool, ShareBuzz, (std::unique_ptr<Buzz> buzz, int64_t timestamp), - (override)); -}; -``` - -Now that we have the mock class defined, we can use it in tests. In the -following code examples, we assume that we have defined a `MockBuzzer` object -named `mock_buzzer_`: - -```cpp - MockBuzzer mock_buzzer_; -``` - -First let’s see how we can set expectations on the `MakeBuzz()` method, which -returns a `unique_ptr<Buzz>`. - -As usual, if you set an expectation without an action (i.e. the `.WillOnce()` or -`.WillRepeatedly()` clause), when that expectation fires, the default action for -that method will be taken. Since `unique_ptr<>` has a default constructor that -returns a null `unique_ptr`, that’s what you’ll get if you don’t specify an -action: - -```cpp - // Use the default action. - EXPECT_CALL(mock_buzzer_, MakeBuzz("hello")); - - // Triggers the previous EXPECT_CALL. - EXPECT_EQ(nullptr, mock_buzzer_.MakeBuzz("hello")); -``` - -If you are not happy with the default action, you can tweak it as usual; see -[Setting Default Actions](#OnCall). - -If you just need to return a pre-defined move-only value, you can use the -`Return(ByMove(...))` action: - -```cpp - // When this fires, the unique_ptr<> specified by ByMove(...) will - // be returned. - EXPECT_CALL(mock_buzzer_, MakeBuzz("world")) - .WillOnce(Return(ByMove(MakeUnique<Buzz>(AccessLevel::kInternal)))); - - EXPECT_NE(nullptr, mock_buzzer_.MakeBuzz("world")); -``` - -Note that `ByMove()` is essential here - if you drop it, the code won’t compile. - -Quiz time! What do you think will happen if a `Return(ByMove(...))` action is -performed more than once (e.g. you write `... -.WillRepeatedly(Return(ByMove(...)));`)? Come think of it, after the first time -the action runs, the source value will be consumed (since it’s a move-only -value), so the next time around, there’s no value to move from -- you’ll get a -run-time error that `Return(ByMove(...))` can only be run once. - -If you need your mock method to do more than just moving a pre-defined value, -remember that you can always use a lambda or a callable object, which can do -pretty much anything you want: - -```cpp - EXPECT_CALL(mock_buzzer_, MakeBuzz("x")) - .WillRepeatedly([](StringPiece text) { - return MakeUnique<Buzz>(AccessLevel::kInternal); - }); - - EXPECT_NE(nullptr, mock_buzzer_.MakeBuzz("x")); - EXPECT_NE(nullptr, mock_buzzer_.MakeBuzz("x")); -``` - -Every time this `EXPECT_CALL` fires, a new `unique_ptr<Buzz>` will be created -and returned. You cannot do this with `Return(ByMove(...))`. - -That covers returning move-only values; but how do we work with methods -accepting move-only arguments? The answer is that they work normally, although -some actions will not compile when any of method's arguments are move-only. You -can always use `Return`, or a [lambda or functor](#FunctionsAsActions): - -```cpp - using ::testing::Unused; - - EXPECT_CALL(mock_buzzer_, ShareBuzz(NotNull(), _)).WillOnce(Return(true)); - EXPECT_TRUE(mock_buzzer_.ShareBuzz(MakeUnique<Buzz>(AccessLevel::kInternal)), - 0); - - EXPECT_CALL(mock_buzzer_, ShareBuzz(_, _)).WillOnce( - [](std::unique_ptr<Buzz> buzz, Unused) { return buzz != nullptr; }); - EXPECT_FALSE(mock_buzzer_.ShareBuzz(nullptr, 0)); -``` - -Many built-in actions (`WithArgs`, `WithoutArgs`,`DeleteArg`, `SaveArg`, ...) -could in principle support move-only arguments, but the support for this is not -implemented yet. If this is blocking you, please file a bug. - -A few actions (e.g. `DoAll`) copy their arguments internally, so they can never -work with non-copyable objects; you'll have to use functors instead. - -#### Legacy workarounds for move-only types {#LegacyMoveOnly} - -Support for move-only function arguments was only introduced to gMock in April -2017. In older code, you may encounter the following workaround for the lack of -this feature (it is no longer necessary - we're including it just for -reference): - -```cpp -class MockBuzzer : public Buzzer { - public: - MOCK_METHOD(bool, DoShareBuzz, (Buzz* buzz, Time timestamp)); - bool ShareBuzz(std::unique_ptr<Buzz> buzz, Time timestamp) override { - return DoShareBuzz(buzz.get(), timestamp); - } -}; -``` - -The trick is to delegate the `ShareBuzz()` method to a mock method (let’s call -it `DoShareBuzz()`) that does not take move-only parameters. Then, instead of -setting expectations on `ShareBuzz()`, you set them on the `DoShareBuzz()` mock -method: - -```cpp - MockBuzzer mock_buzzer_; - EXPECT_CALL(mock_buzzer_, DoShareBuzz(NotNull(), _)); - - // When one calls ShareBuzz() on the MockBuzzer like this, the call is - // forwarded to DoShareBuzz(), which is mocked. Therefore this statement - // will trigger the above EXPECT_CALL. - mock_buzzer_.ShareBuzz(MakeUnique<Buzz>(AccessLevel::kInternal), 0); -``` - -### Making the Compilation Faster - -Believe it or not, the *vast majority* of the time spent on compiling a mock -class is in generating its constructor and destructor, as they perform -non-trivial tasks (e.g. verification of the expectations). What's more, mock -methods with different signatures have different types and thus their -constructors/destructors need to be generated by the compiler separately. As a -result, if you mock many different types of methods, compiling your mock class -can get really slow. - -If you are experiencing slow compilation, you can move the definition of your -mock class' constructor and destructor out of the class body and into a `.cc` -file. This way, even if you `#include` your mock class in N files, the compiler -only needs to generate its constructor and destructor once, resulting in a much -faster compilation. - -Let's illustrate the idea using an example. Here's the definition of a mock -class before applying this recipe: - -```cpp -// File mock_foo.h. -... -class MockFoo : public Foo { - public: - // Since we don't declare the constructor or the destructor, - // the compiler will generate them in every translation unit - // where this mock class is used. - - MOCK_METHOD(int, DoThis, (), (override)); - MOCK_METHOD(bool, DoThat, (const char* str), (override)); - ... more mock methods ... -}; -``` - -After the change, it would look like: - -```cpp -// File mock_foo.h. -... -class MockFoo : public Foo { - public: - // The constructor and destructor are declared, but not defined, here. - MockFoo(); - virtual ~MockFoo(); - - MOCK_METHOD(int, DoThis, (), (override)); - MOCK_METHOD(bool, DoThat, (const char* str), (override)); - ... more mock methods ... -}; -``` - -and - -```cpp -// File mock_foo.cc. -#include "path/to/mock_foo.h" - -// The definitions may appear trivial, but the functions actually do a -// lot of things through the constructors/destructors of the member -// variables used to implement the mock methods. -MockFoo::MockFoo() {} -MockFoo::~MockFoo() {} -``` - -### Forcing a Verification - -When it's being destroyed, your friendly mock object will automatically verify -that all expectations on it have been satisfied, and will generate googletest -failures if not. This is convenient as it leaves you with one less thing to -worry about. That is, unless you are not sure if your mock object will be -destroyed. - -How could it be that your mock object won't eventually be destroyed? Well, it -might be created on the heap and owned by the code you are testing. Suppose -there's a bug in that code and it doesn't delete the mock object properly - you -could end up with a passing test when there's actually a bug. - -Using a heap checker is a good idea and can alleviate the concern, but its -implementation is not 100% reliable. So, sometimes you do want to *force* gMock -to verify a mock object before it is (hopefully) destructed. You can do this -with `Mock::VerifyAndClearExpectations(&mock_object)`: - -```cpp -TEST(MyServerTest, ProcessesRequest) { - using ::testing::Mock; - - MockFoo* const foo = new MockFoo; - EXPECT_CALL(*foo, ...)...; - // ... other expectations ... - - // server now owns foo. - MyServer server(foo); - server.ProcessRequest(...); - - // In case that server's destructor will forget to delete foo, - // this will verify the expectations anyway. - Mock::VerifyAndClearExpectations(foo); -} // server is destroyed when it goes out of scope here. -``` - -**Tip:** The `Mock::VerifyAndClearExpectations()` function returns a `bool` to -indicate whether the verification was successful (`true` for yes), so you can -wrap that function call inside a `ASSERT_TRUE()` if there is no point going -further when the verification has failed. - -### Using Check Points {#UsingCheckPoints} - -Sometimes you may want to "reset" a mock object at various check points in your -test: at each check point, you verify that all existing expectations on the mock -object have been satisfied, and then you set some new expectations on it as if -it's newly created. This allows you to work with a mock object in "phases" whose -sizes are each manageable. - -One such scenario is that in your test's `SetUp()` function, you may want to put -the object you are testing into a certain state, with the help from a mock -object. Once in the desired state, you want to clear all expectations on the -mock, such that in the `TEST_F` body you can set fresh expectations on it. - -As you may have figured out, the `Mock::VerifyAndClearExpectations()` function -we saw in the previous recipe can help you here. Or, if you are using -`ON_CALL()` to set default actions on the mock object and want to clear the -default actions as well, use `Mock::VerifyAndClear(&mock_object)` instead. This -function does what `Mock::VerifyAndClearExpectations(&mock_object)` does and -returns the same `bool`, **plus** it clears the `ON_CALL()` statements on -`mock_object` too. - -Another trick you can use to achieve the same effect is to put the expectations -in sequences and insert calls to a dummy "check-point" function at specific -places. Then you can verify that the mock function calls do happen at the right -time. For example, if you are exercising code: - -```cpp - Foo(1); - Foo(2); - Foo(3); -``` - -and want to verify that `Foo(1)` and `Foo(3)` both invoke `mock.Bar("a")`, but -`Foo(2)` doesn't invoke anything. You can write: - -```cpp -using ::testing::MockFunction; - -TEST(FooTest, InvokesBarCorrectly) { - MyMock mock; - // Class MockFunction<F> has exactly one mock method. It is named - // Call() and has type F. - MockFunction<void(string check_point_name)> check; - { - InSequence s; - - EXPECT_CALL(mock, Bar("a")); - EXPECT_CALL(check, Call("1")); - EXPECT_CALL(check, Call("2")); - EXPECT_CALL(mock, Bar("a")); - } - Foo(1); - check.Call("1"); - Foo(2); - check.Call("2"); - Foo(3); -} -``` - -The expectation spec says that the first `Bar("a")` must happen before check -point "1", the second `Bar("a")` must happen after check point "2", and nothing -should happen between the two check points. The explicit check points make it -easy to tell which `Bar("a")` is called by which call to `Foo()`. - -### Mocking Destructors - -Sometimes you want to make sure a mock object is destructed at the right time, -e.g. after `bar->A()` is called but before `bar->B()` is called. We already know -that you can specify constraints on the [order](#OrderedCalls) of mock function -calls, so all we need to do is to mock the destructor of the mock function. - -This sounds simple, except for one problem: a destructor is a special function -with special syntax and special semantics, and the `MOCK_METHOD` macro doesn't -work for it: - -```cpp -MOCK_METHOD(void, ~MockFoo, ()); // Won't compile! -``` - -The good news is that you can use a simple pattern to achieve the same effect. -First, add a mock function `Die()` to your mock class and call it in the -destructor, like this: - -```cpp -class MockFoo : public Foo { - ... - // Add the following two lines to the mock class. - MOCK_METHOD(void, Die, ()); - ~MockFoo() override { Die(); } -}; -``` - -(If the name `Die()` clashes with an existing symbol, choose another name.) Now, -we have translated the problem of testing when a `MockFoo` object dies to -testing when its `Die()` method is called: - -```cpp - MockFoo* foo = new MockFoo; - MockBar* bar = new MockBar; - ... - { - InSequence s; - - // Expects *foo to die after bar->A() and before bar->B(). - EXPECT_CALL(*bar, A()); - EXPECT_CALL(*foo, Die()); - EXPECT_CALL(*bar, B()); - } -``` - -And that's that. - -### Using gMock and Threads {#UsingThreads} - -In a **unit** test, it's best if you could isolate and test a piece of code in a -single-threaded context. That avoids race conditions and dead locks, and makes -debugging your test much easier. - -Yet most programs are multi-threaded, and sometimes to test something we need to -pound on it from more than one thread. gMock works for this purpose too. - -Remember the steps for using a mock: - -1. Create a mock object `foo`. -2. Set its default actions and expectations using `ON_CALL()` and - `EXPECT_CALL()`. -3. The code under test calls methods of `foo`. -4. Optionally, verify and reset the mock. -5. Destroy the mock yourself, or let the code under test destroy it. The - destructor will automatically verify it. - -If you follow the following simple rules, your mocks and threads can live -happily together: - -* Execute your *test code* (as opposed to the code being tested) in *one* - thread. This makes your test easy to follow. -* Obviously, you can do step #1 without locking. -* When doing step #2 and #5, make sure no other thread is accessing `foo`. - Obvious too, huh? -* #3 and #4 can be done either in one thread or in multiple threads - anyway - you want. gMock takes care of the locking, so you don't have to do any - - unless required by your test logic. - -If you violate the rules (for example, if you set expectations on a mock while -another thread is calling its methods), you get undefined behavior. That's not -fun, so don't do it. - -gMock guarantees that the action for a mock function is done in the same thread -that called the mock function. For example, in - -```cpp - EXPECT_CALL(mock, Foo(1)) - .WillOnce(action1); - EXPECT_CALL(mock, Foo(2)) - .WillOnce(action2); -``` - -if `Foo(1)` is called in thread 1 and `Foo(2)` is called in thread 2, gMock will -execute `action1` in thread 1 and `action2` in thread 2. - -gMock does *not* impose a sequence on actions performed in different threads -(doing so may create deadlocks as the actions may need to cooperate). This means -that the execution of `action1` and `action2` in the above example *may* -interleave. If this is a problem, you should add proper synchronization logic to -`action1` and `action2` to make the test thread-safe. - -Also, remember that `DefaultValue<T>` is a global resource that potentially -affects *all* living mock objects in your program. Naturally, you won't want to -mess with it from multiple threads or when there still are mocks in action. - -### Controlling How Much Information gMock Prints - -When gMock sees something that has the potential of being an error (e.g. a mock -function with no expectation is called, a.k.a. an uninteresting call, which is -allowed but perhaps you forgot to explicitly ban the call), it prints some -warning messages, including the arguments of the function, the return value, and -the stack trace. Hopefully this will remind you to take a look and see if there -is indeed a problem. - -Sometimes you are confident that your tests are correct and may not appreciate -such friendly messages. Some other times, you are debugging your tests or -learning about the behavior of the code you are testing, and wish you could -observe every mock call that happens (including argument values, the return -value, and the stack trace). Clearly, one size doesn't fit all. - -You can control how much gMock tells you using the `--gmock_verbose=LEVEL` -command-line flag, where `LEVEL` is a string with three possible values: - -* `info`: gMock will print all informational messages, warnings, and errors - (most verbose). At this setting, gMock will also log any calls to the - `ON_CALL/EXPECT_CALL` macros. It will include a stack trace in - "uninteresting call" warnings. -* `warning`: gMock will print both warnings and errors (less verbose); it will - omit the stack traces in "uninteresting call" warnings. This is the default. -* `error`: gMock will print errors only (least verbose). - -Alternatively, you can adjust the value of that flag from within your tests like -so: - -```cpp - ::testing::FLAGS_gmock_verbose = "error"; -``` - -If you find gMock printing too many stack frames with its informational or -warning messages, remember that you can control their amount with the -`--gtest_stack_trace_depth=max_depth` flag. - -Now, judiciously use the right flag to enable gMock serve you better! - -### Gaining Super Vision into Mock Calls - -You have a test using gMock. It fails: gMock tells you some expectations aren't -satisfied. However, you aren't sure why: Is there a typo somewhere in the -matchers? Did you mess up the order of the `EXPECT_CALL`s? Or is the code under -test doing something wrong? How can you find out the cause? - -Won't it be nice if you have X-ray vision and can actually see the trace of all -`EXPECT_CALL`s and mock method calls as they are made? For each call, would you -like to see its actual argument values and which `EXPECT_CALL` gMock thinks it -matches? If you still need some help to figure out who made these calls, how -about being able to see the complete stack trace at each mock call? - -You can unlock this power by running your test with the `--gmock_verbose=info` -flag. For example, given the test program: - -```cpp -#include "gmock/gmock.h" - -using testing::_; -using testing::HasSubstr; -using testing::Return; - -class MockFoo { - public: - MOCK_METHOD(void, F, (const string& x, const string& y)); -}; - -TEST(Foo, Bar) { - MockFoo mock; - EXPECT_CALL(mock, F(_, _)).WillRepeatedly(Return()); - EXPECT_CALL(mock, F("a", "b")); - EXPECT_CALL(mock, F("c", HasSubstr("d"))); - - mock.F("a", "good"); - mock.F("a", "b"); -} -``` - -if you run it with `--gmock_verbose=info`, you will see this output: - -```shell -[ RUN ] Foo.Bar - -foo_test.cc:14: EXPECT_CALL(mock, F(_, _)) invoked -Stack trace: ... - -foo_test.cc:15: EXPECT_CALL(mock, F("a", "b")) invoked -Stack trace: ... - -foo_test.cc:16: EXPECT_CALL(mock, F("c", HasSubstr("d"))) invoked -Stack trace: ... - -foo_test.cc:14: Mock function call matches EXPECT_CALL(mock, F(_, _))... - Function call: F(@0x7fff7c8dad40"a",@0x7fff7c8dad10"good") -Stack trace: ... - -foo_test.cc:15: Mock function call matches EXPECT_CALL(mock, F("a", "b"))... - Function call: F(@0x7fff7c8dada0"a",@0x7fff7c8dad70"b") -Stack trace: ... - -foo_test.cc:16: Failure -Actual function call count doesn't match EXPECT_CALL(mock, F("c", HasSubstr("d")))... - Expected: to be called once - Actual: never called - unsatisfied and active -[ FAILED ] Foo.Bar -``` - -Suppose the bug is that the `"c"` in the third `EXPECT_CALL` is a typo and -should actually be `"a"`. With the above message, you should see that the actual -`F("a", "good")` call is matched by the first `EXPECT_CALL`, not the third as -you thought. From that it should be obvious that the third `EXPECT_CALL` is -written wrong. Case solved. - -If you are interested in the mock call trace but not the stack traces, you can -combine `--gmock_verbose=info` with `--gtest_stack_trace_depth=0` on the test -command line. - -<!-- GOOGLETEST_CM0025 DO NOT DELETE --> - -### Running Tests in Emacs - -If you build and run your tests in Emacs using the `M-x google-compile` command -(as many googletest users do), the source file locations of gMock and googletest -errors will be highlighted. Just press `<Enter>` on one of them and you'll be -taken to the offending line. Or, you can just type `C-x`` to jump to the next -error. - -To make it even easier, you can add the following lines to your `~/.emacs` file: - -```text -(global-set-key "\M-m" 'google-compile) ; m is for make -(global-set-key [M-down] 'next-error) -(global-set-key [M-up] '(lambda () (interactive) (next-error -1))) -``` - -Then you can type `M-m` to start a build (if you want to run the test as well, -just make sure `foo_test.run` or `runtests` is in the build command you supply -after typing `M-m`), or `M-up`/`M-down` to move back and forth between errors. - -## Extending gMock - -### Writing New Matchers Quickly {#NewMatchers} - -WARNING: gMock does not guarantee when or how many times a matcher will be -invoked. Therefore, all matchers must be functionally pure. See -[this section](#PureMatchers) for more details. - -The `MATCHER*` family of macros can be used to define custom matchers easily. -The syntax: - -```cpp -MATCHER(name, description_string_expression) { statements; } -``` - -will define a matcher with the given name that executes the statements, which -must return a `bool` to indicate if the match succeeds. Inside the statements, -you can refer to the value being matched by `arg`, and refer to its type by -`arg_type`. - -The *description string* is a `string`-typed expression that documents what the -matcher does, and is used to generate the failure message when the match fails. -It can (and should) reference the special `bool` variable `negation`, and should -evaluate to the description of the matcher when `negation` is `false`, or that -of the matcher's negation when `negation` is `true`. - -For convenience, we allow the description string to be empty (`""`), in which -case gMock will use the sequence of words in the matcher name as the -description. - -For example: - -```cpp -MATCHER(IsDivisibleBy7, "") { return (arg % 7) == 0; } -``` - -allows you to write - -```cpp - // Expects mock_foo.Bar(n) to be called where n is divisible by 7. - EXPECT_CALL(mock_foo, Bar(IsDivisibleBy7())); -``` - -or, - -```cpp - using ::testing::Not; - ... - // Verifies that two values are divisible by 7. - EXPECT_THAT(some_expression, IsDivisibleBy7()); - EXPECT_THAT(some_other_expression, Not(IsDivisibleBy7())); -``` - -If the above assertions fail, they will print something like: - -```shell - Value of: some_expression - Expected: is divisible by 7 - Actual: 27 - ... - Value of: some_other_expression - Expected: not (is divisible by 7) - Actual: 21 -``` - -where the descriptions `"is divisible by 7"` and `"not (is divisible by 7)"` are -automatically calculated from the matcher name `IsDivisibleBy7`. - -As you may have noticed, the auto-generated descriptions (especially those for -the negation) may not be so great. You can always override them with a `string` -expression of your own: - -```cpp -MATCHER(IsDivisibleBy7, - absl::StrCat(negation ? "isn't" : "is", " divisible by 7")) { - return (arg % 7) == 0; -} -``` - -Optionally, you can stream additional information to a hidden argument named -`result_listener` to explain the match result. For example, a better definition -of `IsDivisibleBy7` is: - -```cpp -MATCHER(IsDivisibleBy7, "") { - if ((arg % 7) == 0) - return true; - - *result_listener << "the remainder is " << (arg % 7); - return false; -} -``` - -With this definition, the above assertion will give a better message: - -```shell - Value of: some_expression - Expected: is divisible by 7 - Actual: 27 (the remainder is 6) -``` - -You should let `MatchAndExplain()` print *any additional information* that can -help a user understand the match result. Note that it should explain why the -match succeeds in case of a success (unless it's obvious) - this is useful when -the matcher is used inside `Not()`. There is no need to print the argument value -itself, as gMock already prints it for you. - -NOTE: The type of the value being matched (`arg_type`) is determined by the -context in which you use the matcher and is supplied to you by the compiler, so -you don't need to worry about declaring it (nor can you). This allows the -matcher to be polymorphic. For example, `IsDivisibleBy7()` can be used to match -any type where the value of `(arg % 7) == 0` can be implicitly converted to a -`bool`. In the `Bar(IsDivisibleBy7())` example above, if method `Bar()` takes an -`int`, `arg_type` will be `int`; if it takes an `unsigned long`, `arg_type` will -be `unsigned long`; and so on. - -### Writing New Parameterized Matchers Quickly - -Sometimes you'll want to define a matcher that has parameters. For that you can -use the macro: - -```cpp -MATCHER_P(name, param_name, description_string) { statements; } -``` - -where the description string can be either `""` or a `string` expression that -references `negation` and `param_name`. - -For example: - -```cpp -MATCHER_P(HasAbsoluteValue, value, "") { return abs(arg) == value; } -``` - -will allow you to write: - -```cpp - EXPECT_THAT(Blah("a"), HasAbsoluteValue(n)); -``` - -which may lead to this message (assuming `n` is 10): - -```shell - Value of: Blah("a") - Expected: has absolute value 10 - Actual: -9 -``` - -Note that both the matcher description and its parameter are printed, making the -message human-friendly. - -In the matcher definition body, you can write `foo_type` to reference the type -of a parameter named `foo`. For example, in the body of -`MATCHER_P(HasAbsoluteValue, value)` above, you can write `value_type` to refer -to the type of `value`. - -gMock also provides `MATCHER_P2`, `MATCHER_P3`, ..., up to `MATCHER_P10` to -support multi-parameter matchers: - -```cpp -MATCHER_Pk(name, param_1, ..., param_k, description_string) { statements; } -``` - -Please note that the custom description string is for a particular *instance* of -the matcher, where the parameters have been bound to actual values. Therefore -usually you'll want the parameter values to be part of the description. gMock -lets you do that by referencing the matcher parameters in the description string -expression. - -For example, - -```cpp -using ::testing::PrintToString; -MATCHER_P2(InClosedRange, low, hi, - absl::StrFormat("%s in range [%s, %s]", negation ? "isn't" : "is", - PrintToString(low), PrintToString(hi))) { - return low <= arg && arg <= hi; -} -... -EXPECT_THAT(3, InClosedRange(4, 6)); -``` - -would generate a failure that contains the message: - -```shell - Expected: is in range [4, 6] -``` - -If you specify `""` as the description, the failure message will contain the -sequence of words in the matcher name followed by the parameter values printed -as a tuple. For example, - -```cpp - MATCHER_P2(InClosedRange, low, hi, "") { ... } - ... - EXPECT_THAT(3, InClosedRange(4, 6)); -``` - -would generate a failure that contains the text: - -```shell - Expected: in closed range (4, 6) -``` - -For the purpose of typing, you can view - -```cpp -MATCHER_Pk(Foo, p1, ..., pk, description_string) { ... } -``` - -as shorthand for - -```cpp -template <typename p1_type, ..., typename pk_type> -FooMatcherPk<p1_type, ..., pk_type> -Foo(p1_type p1, ..., pk_type pk) { ... } -``` - -When you write `Foo(v1, ..., vk)`, the compiler infers the types of the -parameters `v1`, ..., and `vk` for you. If you are not happy with the result of -the type inference, you can specify the types by explicitly instantiating the -template, as in `Foo<long, bool>(5, false)`. As said earlier, you don't get to -(or need to) specify `arg_type` as that's determined by the context in which the -matcher is used. - -You can assign the result of expression `Foo(p1, ..., pk)` to a variable of type -`FooMatcherPk<p1_type, ..., pk_type>`. This can be useful when composing -matchers. Matchers that don't have a parameter or have only one parameter have -special types: you can assign `Foo()` to a `FooMatcher`-typed variable, and -assign `Foo(p)` to a `FooMatcherP<p_type>`-typed variable. - -While you can instantiate a matcher template with reference types, passing the -parameters by pointer usually makes your code more readable. If, however, you -still want to pass a parameter by reference, be aware that in the failure -message generated by the matcher you will see the value of the referenced object -but not its address. - -You can overload matchers with different numbers of parameters: - -```cpp -MATCHER_P(Blah, a, description_string_1) { ... } -MATCHER_P2(Blah, a, b, description_string_2) { ... } -``` - -While it's tempting to always use the `MATCHER*` macros when defining a new -matcher, you should also consider implementing `MatcherInterface` or using -`MakePolymorphicMatcher()` instead (see the recipes that follow), especially if -you need to use the matcher a lot. While these approaches require more work, -they give you more control on the types of the value being matched and the -matcher parameters, which in general leads to better compiler error messages -that pay off in the long run. They also allow overloading matchers based on -parameter types (as opposed to just based on the number of parameters). - -### Writing New Monomorphic Matchers - -A matcher of argument type `T` implements `::testing::MatcherInterface<T>` and -does two things: it tests whether a value of type `T` matches the matcher, and -can describe what kind of values it matches. The latter ability is used for -generating readable error messages when expectations are violated. - -The interface looks like this: - -```cpp -class MatchResultListener { - public: - ... - // Streams x to the underlying ostream; does nothing if the ostream - // is NULL. - template <typename T> - MatchResultListener& operator<<(const T& x); - - // Returns the underlying ostream. - std::ostream* stream(); -}; - -template <typename T> -class MatcherInterface { - public: - virtual ~MatcherInterface(); - - // Returns true if and only if the matcher matches x; also explains the match - // result to 'listener'. - virtual bool MatchAndExplain(T x, MatchResultListener* listener) const = 0; - - // Describes this matcher to an ostream. - virtual void DescribeTo(std::ostream* os) const = 0; - - // Describes the negation of this matcher to an ostream. - virtual void DescribeNegationTo(std::ostream* os) const; -}; -``` - -If you need a custom matcher but `Truly()` is not a good option (for example, -you may not be happy with the way `Truly(predicate)` describes itself, or you -may want your matcher to be polymorphic as `Eq(value)` is), you can define a -matcher to do whatever you want in two steps: first implement the matcher -interface, and then define a factory function to create a matcher instance. The -second step is not strictly needed but it makes the syntax of using the matcher -nicer. - -For example, you can define a matcher to test whether an `int` is divisible by 7 -and then use it like this: - -```cpp -using ::testing::MakeMatcher; -using ::testing::Matcher; -using ::testing::MatcherInterface; -using ::testing::MatchResultListener; - -class DivisibleBy7Matcher : public MatcherInterface<int> { - public: - bool MatchAndExplain(int n, - MatchResultListener* /* listener */) const override { - return (n % 7) == 0; - } - - void DescribeTo(std::ostream* os) const override { - *os << "is divisible by 7"; - } - - void DescribeNegationTo(std::ostream* os) const override { - *os << "is not divisible by 7"; - } -}; - -Matcher<int> DivisibleBy7() { - return MakeMatcher(new DivisibleBy7Matcher); -} - -... - EXPECT_CALL(foo, Bar(DivisibleBy7())); -``` - -You may improve the matcher message by streaming additional information to the -`listener` argument in `MatchAndExplain()`: - -```cpp -class DivisibleBy7Matcher : public MatcherInterface<int> { - public: - bool MatchAndExplain(int n, - MatchResultListener* listener) const override { - const int remainder = n % 7; - if (remainder != 0) { - *listener << "the remainder is " << remainder; - } - return remainder == 0; - } - ... -}; -``` - -Then, `EXPECT_THAT(x, DivisibleBy7());` may generate a message like this: - -```shell -Value of: x -Expected: is divisible by 7 - Actual: 23 (the remainder is 2) -``` - -### Writing New Polymorphic Matchers - -You've learned how to write your own matchers in the previous recipe. Just one -problem: a matcher created using `MakeMatcher()` only works for one particular -type of arguments. If you want a *polymorphic* matcher that works with arguments -of several types (for instance, `Eq(x)` can be used to match a *`value`* as long -as `value == x` compiles -- *`value`* and `x` don't have to share the same -type), you can learn the trick from `testing/base/public/gmock-matchers.h` but -it's a bit involved. - -Fortunately, most of the time you can define a polymorphic matcher easily with -the help of `MakePolymorphicMatcher()`. Here's how you can define `NotNull()` as -an example: - -```cpp -using ::testing::MakePolymorphicMatcher; -using ::testing::MatchResultListener; -using ::testing::PolymorphicMatcher; - -class NotNullMatcher { - public: - // To implement a polymorphic matcher, first define a COPYABLE class - // that has three members MatchAndExplain(), DescribeTo(), and - // DescribeNegationTo(), like the following. - - // In this example, we want to use NotNull() with any pointer, so - // MatchAndExplain() accepts a pointer of any type as its first argument. - // In general, you can define MatchAndExplain() as an ordinary method or - // a method template, or even overload it. - template <typename T> - bool MatchAndExplain(T* p, - MatchResultListener* /* listener */) const { - return p != NULL; - } - - // Describes the property of a value matching this matcher. - void DescribeTo(std::ostream* os) const { *os << "is not NULL"; } - - // Describes the property of a value NOT matching this matcher. - void DescribeNegationTo(std::ostream* os) const { *os << "is NULL"; } -}; - -// To construct a polymorphic matcher, pass an instance of the class -// to MakePolymorphicMatcher(). Note the return type. -PolymorphicMatcher<NotNullMatcher> NotNull() { - return MakePolymorphicMatcher(NotNullMatcher()); -} - -... - - EXPECT_CALL(foo, Bar(NotNull())); // The argument must be a non-NULL pointer. -``` - -**Note:** Your polymorphic matcher class does **not** need to inherit from -`MatcherInterface` or any other class, and its methods do **not** need to be -virtual. - -Like in a monomorphic matcher, you may explain the match result by streaming -additional information to the `listener` argument in `MatchAndExplain()`. - -### Writing New Cardinalities - -A cardinality is used in `Times()` to tell gMock how many times you expect a -call to occur. It doesn't have to be exact. For example, you can say -`AtLeast(5)` or `Between(2, 4)`. - -If the [built-in set](cheat_sheet.md#CardinalityList) of cardinalities doesn't -suit you, you are free to define your own by implementing the following -interface (in namespace `testing`): - -```cpp -class CardinalityInterface { - public: - virtual ~CardinalityInterface(); - - // Returns true if and only if call_count calls will satisfy this cardinality. - virtual bool IsSatisfiedByCallCount(int call_count) const = 0; - - // Returns true if and only if call_count calls will saturate this - // cardinality. - virtual bool IsSaturatedByCallCount(int call_count) const = 0; - - // Describes self to an ostream. - virtual void DescribeTo(std::ostream* os) const = 0; -}; -``` - -For example, to specify that a call must occur even number of times, you can -write - -```cpp -using ::testing::Cardinality; -using ::testing::CardinalityInterface; -using ::testing::MakeCardinality; - -class EvenNumberCardinality : public CardinalityInterface { - public: - bool IsSatisfiedByCallCount(int call_count) const override { - return (call_count % 2) == 0; - } - - bool IsSaturatedByCallCount(int call_count) const override { - return false; - } - - void DescribeTo(std::ostream* os) const { - *os << "called even number of times"; - } -}; - -Cardinality EvenNumber() { - return MakeCardinality(new EvenNumberCardinality); -} - -... - EXPECT_CALL(foo, Bar(3)) - .Times(EvenNumber()); -``` - -### Writing New Actions Quickly {#QuickNewActions} - -If the built-in actions don't work for you, you can easily define your own one. -Just define a functor class with a (possibly templated) call operator, matching -the signature of your action. - -```cpp -struct Increment { - template <typename T> - T operator()(T* arg) { - return ++(*arg); - } -} -``` - -The same approach works with stateful functors (or any callable, really): - -``` -struct MultiplyBy { - template <typename T> - T operator()(T arg) { return arg * multiplier; } - - int multiplier; -} - -// Then use: -// EXPECT_CALL(...).WillOnce(MultiplyBy{7}); -``` - -#### Legacy macro-based Actions - -Before C++11, the functor-based actions were not supported; the old way of -writing actions was through a set of `ACTION*` macros. We suggest to avoid them -in new code; they hide a lot of logic behind the macro, potentially leading to -harder-to-understand compiler errors. Nevertheless, we cover them here for -completeness. - -By writing - -```cpp -ACTION(name) { statements; } -``` - -in a namespace scope (i.e. not inside a class or function), you will define an -action with the given name that executes the statements. The value returned by -`statements` will be used as the return value of the action. Inside the -statements, you can refer to the K-th (0-based) argument of the mock function as -`argK`. For example: - -```cpp -ACTION(IncrementArg1) { return ++(*arg1); } -``` - -allows you to write - -```cpp -... WillOnce(IncrementArg1()); -``` - -Note that you don't need to specify the types of the mock function arguments. -Rest assured that your code is type-safe though: you'll get a compiler error if -`*arg1` doesn't support the `++` operator, or if the type of `++(*arg1)` isn't -compatible with the mock function's return type. - -Another example: - -```cpp -ACTION(Foo) { - (*arg2)(5); - Blah(); - *arg1 = 0; - return arg0; -} -``` - -defines an action `Foo()` that invokes argument #2 (a function pointer) with 5, -calls function `Blah()`, sets the value pointed to by argument #1 to 0, and -returns argument #0. - -For more convenience and flexibility, you can also use the following pre-defined -symbols in the body of `ACTION`: - -`argK_type` | The type of the K-th (0-based) argument of the mock function -:-------------- | :----------------------------------------------------------- -`args` | All arguments of the mock function as a tuple -`args_type` | The type of all arguments of the mock function as a tuple -`return_type` | The return type of the mock function -`function_type` | The type of the mock function - -For example, when using an `ACTION` as a stub action for mock function: - -```cpp -int DoSomething(bool flag, int* ptr); -``` - -we have: - -Pre-defined Symbol | Is Bound To ------------------- | --------------------------------- -`arg0` | the value of `flag` -`arg0_type` | the type `bool` -`arg1` | the value of `ptr` -`arg1_type` | the type `int*` -`args` | the tuple `(flag, ptr)` -`args_type` | the type `std::tuple<bool, int*>` -`return_type` | the type `int` -`function_type` | the type `int(bool, int*)` - -#### Legacy macro-based parameterized Actions - -Sometimes you'll want to parameterize an action you define. For that we have -another macro - -```cpp -ACTION_P(name, param) { statements; } -``` - -For example, - -```cpp -ACTION_P(Add, n) { return arg0 + n; } -``` - -will allow you to write - -```cpp -// Returns argument #0 + 5. -... WillOnce(Add(5)); -``` - -For convenience, we use the term *arguments* for the values used to invoke the -mock function, and the term *parameters* for the values used to instantiate an -action. - -Note that you don't need to provide the type of the parameter either. Suppose -the parameter is named `param`, you can also use the gMock-defined symbol -`param_type` to refer to the type of the parameter as inferred by the compiler. -For example, in the body of `ACTION_P(Add, n)` above, you can write `n_type` for -the type of `n`. - -gMock also provides `ACTION_P2`, `ACTION_P3`, and etc to support multi-parameter -actions. For example, - -```cpp -ACTION_P2(ReturnDistanceTo, x, y) { - double dx = arg0 - x; - double dy = arg1 - y; - return sqrt(dx*dx + dy*dy); -} -``` - -lets you write - -```cpp -... WillOnce(ReturnDistanceTo(5.0, 26.5)); -``` - -You can view `ACTION` as a degenerated parameterized action where the number of -parameters is 0. - -You can also easily define actions overloaded on the number of parameters: - -```cpp -ACTION_P(Plus, a) { ... } -ACTION_P2(Plus, a, b) { ... } -``` - -### Restricting the Type of an Argument or Parameter in an ACTION - -For maximum brevity and reusability, the `ACTION*` macros don't ask you to -provide the types of the mock function arguments and the action parameters. -Instead, we let the compiler infer the types for us. - -Sometimes, however, we may want to be more explicit about the types. There are -several tricks to do that. For example: - -```cpp -ACTION(Foo) { - // Makes sure arg0 can be converted to int. - int n = arg0; - ... use n instead of arg0 here ... -} - -ACTION_P(Bar, param) { - // Makes sure the type of arg1 is const char*. - ::testing::StaticAssertTypeEq<const char*, arg1_type>(); - - // Makes sure param can be converted to bool. - bool flag = param; -} -``` - -where `StaticAssertTypeEq` is a compile-time assertion in googletest that -verifies two types are the same. - -### Writing New Action Templates Quickly - -Sometimes you want to give an action explicit template parameters that cannot be -inferred from its value parameters. `ACTION_TEMPLATE()` supports that and can be -viewed as an extension to `ACTION()` and `ACTION_P*()`. - -The syntax: - -```cpp -ACTION_TEMPLATE(ActionName, - HAS_m_TEMPLATE_PARAMS(kind1, name1, ..., kind_m, name_m), - AND_n_VALUE_PARAMS(p1, ..., p_n)) { statements; } -``` - -defines an action template that takes *m* explicit template parameters and *n* -value parameters, where *m* is in [1, 10] and *n* is in [0, 10]. `name_i` is the -name of the *i*-th template parameter, and `kind_i` specifies whether it's a -`typename`, an integral constant, or a template. `p_i` is the name of the *i*-th -value parameter. - -Example: - -```cpp -// DuplicateArg<k, T>(output) converts the k-th argument of the mock -// function to type T and copies it to *output. -ACTION_TEMPLATE(DuplicateArg, - // Note the comma between int and k: - HAS_2_TEMPLATE_PARAMS(int, k, typename, T), - AND_1_VALUE_PARAMS(output)) { - *output = T(std::get<k>(args)); -} -``` - -To create an instance of an action template, write: - -```cpp -ActionName<t1, ..., t_m>(v1, ..., v_n) -``` - -where the `t`s are the template arguments and the `v`s are the value arguments. -The value argument types are inferred by the compiler. For example: - -```cpp -using ::testing::_; -... - int n; - EXPECT_CALL(mock, Foo).WillOnce(DuplicateArg<1, unsigned char>(&n)); -``` - -If you want to explicitly specify the value argument types, you can provide -additional template arguments: - -```cpp -ActionName<t1, ..., t_m, u1, ..., u_k>(v1, ..., v_n) -``` - -where `u_i` is the desired type of `v_i`. - -`ACTION_TEMPLATE` and `ACTION`/`ACTION_P*` can be overloaded on the number of -value parameters, but not on the number of template parameters. Without the -restriction, the meaning of the following is unclear: - -```cpp - OverloadedAction<int, bool>(x); -``` - -Are we using a single-template-parameter action where `bool` refers to the type -of `x`, or a two-template-parameter action where the compiler is asked to infer -the type of `x`? - -### Using the ACTION Object's Type - -If you are writing a function that returns an `ACTION` object, you'll need to -know its type. The type depends on the macro used to define the action and the -parameter types. The rule is relatively simple: - -| Given Definition | Expression | Has Type | -| ----------------------------- | ------------------- | --------------------- | -| `ACTION(Foo)` | `Foo()` | `FooAction` | -| `ACTION_TEMPLATE(Foo,` | `Foo<t1, ..., | `FooAction<t1, ..., | -: `HAS_m_TEMPLATE_PARAMS(...),` : t_m>()` : t_m>` : -: `AND_0_VALUE_PARAMS())` : : : -| `ACTION_P(Bar, param)` | `Bar(int_value)` | `BarActionP<int>` | -| `ACTION_TEMPLATE(Bar,` | `Bar<t1, ..., t_m>` | `FooActionP<t1, ..., | -: `HAS_m_TEMPLATE_PARAMS(...),` : `(int_value)` : t_m, int>` : -: `AND_1_VALUE_PARAMS(p1))` : : : -| `ACTION_P2(Baz, p1, p2)` | `Baz(bool_value,` | `BazActionP2<bool, | -: : `int_value)` : int>` : -| `ACTION_TEMPLATE(Baz,` | `Baz<t1, ..., t_m>` | `FooActionP2<t1, ..., | -: `HAS_m_TEMPLATE_PARAMS(...),` : `(bool_value,` : t_m,` `bool, int>` : -: `AND_2_VALUE_PARAMS(p1, p2))` : `int_value)` : : -| ... | ... | ... | - -Note that we have to pick different suffixes (`Action`, `ActionP`, `ActionP2`, -and etc) for actions with different numbers of value parameters, or the action -definitions cannot be overloaded on the number of them. - -### Writing New Monomorphic Actions {#NewMonoActions} - -While the `ACTION*` macros are very convenient, sometimes they are -inappropriate. For example, despite the tricks shown in the previous recipes, -they don't let you directly specify the types of the mock function arguments and -the action parameters, which in general leads to unoptimized compiler error -messages that can baffle unfamiliar users. They also don't allow overloading -actions based on parameter types without jumping through some hoops. - -An alternative to the `ACTION*` macros is to implement -`::testing::ActionInterface<F>`, where `F` is the type of the mock function in -which the action will be used. For example: - -```cpp -template <typename F> -class ActionInterface { - public: - virtual ~ActionInterface(); - - // Performs the action. Result is the return type of function type - // F, and ArgumentTuple is the tuple of arguments of F. - // - - // For example, if F is int(bool, const string&), then Result would - // be int, and ArgumentTuple would be std::tuple<bool, const string&>. - virtual Result Perform(const ArgumentTuple& args) = 0; -}; -``` - -```cpp -using ::testing::_; -using ::testing::Action; -using ::testing::ActionInterface; -using ::testing::MakeAction; - -typedef int IncrementMethod(int*); - -class IncrementArgumentAction : public ActionInterface<IncrementMethod> { - public: - int Perform(const std::tuple<int*>& args) override { - int* p = std::get<0>(args); // Grabs the first argument. - return *p++; - } -}; - -Action<IncrementMethod> IncrementArgument() { - return MakeAction(new IncrementArgumentAction); -} - -... - EXPECT_CALL(foo, Baz(_)) - .WillOnce(IncrementArgument()); - - int n = 5; - foo.Baz(&n); // Should return 5 and change n to 6. -``` - -### Writing New Polymorphic Actions {#NewPolyActions} - -The previous recipe showed you how to define your own action. This is all good, -except that you need to know the type of the function in which the action will -be used. Sometimes that can be a problem. For example, if you want to use the -action in functions with *different* types (e.g. like `Return()` and -`SetArgPointee()`). - -If an action can be used in several types of mock functions, we say it's -*polymorphic*. The `MakePolymorphicAction()` function template makes it easy to -define such an action: - -```cpp -namespace testing { -template <typename Impl> -PolymorphicAction<Impl> MakePolymorphicAction(const Impl& impl); -} // namespace testing -``` - -As an example, let's define an action that returns the second argument in the -mock function's argument list. The first step is to define an implementation -class: - -```cpp -class ReturnSecondArgumentAction { - public: - template <typename Result, typename ArgumentTuple> - Result Perform(const ArgumentTuple& args) const { - // To get the i-th (0-based) argument, use std::get(args). - return std::get<1>(args); - } -}; -``` - -This implementation class does *not* need to inherit from any particular class. -What matters is that it must have a `Perform()` method template. This method -template takes the mock function's arguments as a tuple in a **single** -argument, and returns the result of the action. It can be either `const` or not, -but must be invokable with exactly one template argument, which is the result -type. In other words, you must be able to call `Perform<R>(args)` where `R` is -the mock function's return type and `args` is its arguments in a tuple. - -Next, we use `MakePolymorphicAction()` to turn an instance of the implementation -class into the polymorphic action we need. It will be convenient to have a -wrapper for this: - -```cpp -using ::testing::MakePolymorphicAction; -using ::testing::PolymorphicAction; - -PolymorphicAction<ReturnSecondArgumentAction> ReturnSecondArgument() { - return MakePolymorphicAction(ReturnSecondArgumentAction()); -} -``` - -Now, you can use this polymorphic action the same way you use the built-in ones: - -```cpp -using ::testing::_; - -class MockFoo : public Foo { - public: - MOCK_METHOD(int, DoThis, (bool flag, int n), (override)); - MOCK_METHOD(string, DoThat, (int x, const char* str1, const char* str2), - (override)); -}; - - ... - MockFoo foo; - EXPECT_CALL(foo, DoThis).WillOnce(ReturnSecondArgument()); - EXPECT_CALL(foo, DoThat).WillOnce(ReturnSecondArgument()); - ... - foo.DoThis(true, 5); // Will return 5. - foo.DoThat(1, "Hi", "Bye"); // Will return "Hi". -``` - -### Teaching gMock How to Print Your Values - -When an uninteresting or unexpected call occurs, gMock prints the argument -values and the stack trace to help you debug. Assertion macros like -`EXPECT_THAT` and `EXPECT_EQ` also print the values in question when the -assertion fails. gMock and googletest do this using googletest's user-extensible -value printer. - -This printer knows how to print built-in C++ types, native arrays, STL -containers, and any type that supports the `<<` operator. For other types, it -prints the raw bytes in the value and hopes that you the user can figure it out. -[googletest's advanced guide](../../googletest/docs/advanced.md#teaching-googletest-how-to-print-your-values) -explains how to extend the printer to do a better job at printing your -particular type than to dump the bytes. - -## Useful Mocks Created Using gMock - -<!--#include file="includes/g3_testing_LOGs.md"--> -<!--#include file="includes/g3_mock_callbacks.md"--> - -### Mock std::function {#MockFunction} - -`std::function` is a general function type introduced in C++11. It is a -preferred way of passing callbacks to new interfaces. Functions are copiable, -and are not usually passed around by pointer, which makes them tricky to mock. -But fear not - `MockFunction` can help you with that. - -`MockFunction<R(T1, ..., Tn)>` has a mock method `Call()` with the signature: - -```cpp - R Call(T1, ..., Tn); -``` - -It also has a `AsStdFunction()` method, which creates a `std::function` proxy -forwarding to Call: - -```cpp - std::function<R(T1, ..., Tn)> AsStdFunction(); -``` - -To use `MockFunction`, first create `MockFunction` object and set up -expectations on its `Call` method. Then pass proxy obtained from -`AsStdFunction()` to the code you are testing. For example: - -```cpp -TEST(FooTest, RunsCallbackWithBarArgument) { - // 1. Create a mock object. - MockFunction<int(string)> mock_function; - - // 2. Set expectations on Call() method. - EXPECT_CALL(mock_function, Call("bar")).WillOnce(Return(1)); - - // 3. Exercise code that uses std::function. - Foo(mock_function.AsStdFunction()); - // Foo's signature can be either of: - // void Foo(const std::function<int(string)>& fun); - // void Foo(std::function<int(string)> fun); - - // 4. All expectations will be verified when mock_function - // goes out of scope and is destroyed. -} -``` - -Remember that function objects created with `AsStdFunction()` are just -forwarders. If you create multiple of them, they will share the same set of -expectations. - -Although `std::function` supports unlimited number of arguments, `MockFunction` -implementation is limited to ten. If you ever hit that limit... well, your -callback has bigger problems than being mockable. :-) - -<!-- GOOGLETEST_CM0034 DO NOT DELETE --> diff --git a/googlemock/docs/design.md b/googlemock/docs/design.md deleted file mode 100644 index 3dd4025..0000000 --- a/googlemock/docs/design.md +++ /dev/null @@ -1,1600 +0,0 @@ -# gMock - a Framework for Writing and Using C++ Mock Classes - -<!--#include file="under-construction-banner.md"--> - -**Status:** Draft \ -**Tiny URL:** http://go/gmockdesign \ -**Author:** Zhanyong Wan (who/wan) - -<!-- GOOGLETEST_CM0035 DO NOT DELETE --> - -(To participate in discussions on gMock, please subscribe to -[opensource-gmock](https://groups.google.com/a/google.com/group/opensource-gmock/subscribe). -Past discussions can be viewed -[here](https://groups.google.com/a/google.com/group/opensource-gmock/topics) and -[here](https://mailman.corp.google.com/pipermail/c-mock-dev/).) - -(The slides for my gMock preview talk can be found here: -[ppt](http://wiki.corp.google.com/twiki/pub/Main/WanTalks/0706-beijing-gmock-preview.ppt).) - -## Objective - -[Mock objects](http://en.wikipedia.org/wiki/Mock_object) are simulated objects -that mimic real objects in controlled ways. They are useful for driving the -design of a system, and for testing some other object when it's difficult to use -real objects in a test. - -While the idea of mocks applies to all objected-oriented languages, writing them -in C++ has many practical difficulties, due to the lack of support for -reflection in the language, the complexity and irregularity of C++, and the lack -of adequate tools. As an unfortunate result, C++ programmers often avoid writing -mocks, resulting in big, monolithic classes in production, and slow, brittle, -and difficult-to-maintain tests. - -We believe that a good framework can make it much more pleasant to write and use -mocks in C++. Such a tool would help people write more -[small](https://wiki.corp.google.com/twiki/bin/view/Main/GoogleTestDefinitions) -tests that are quick, robust, and precise. Perhaps more importantly, -incorporating mocks early and often in the design process helps people discover -the role interfaces in the system and thus often leads to -[better designs](http://www.jmock.org/oopsla2004.pdf). - -We plan to develop *gMock* as a generic framework for creating and using mock -classes in C++. We would encourage people to *use gMock as a design tool as much -as a testing tool*. - -### Goals of gMock - -* **Supporting all interfaces:** A user should be able to use gMock to create - a mock class for any C++ interface (i.e. a class whose methods are virtual). - In particular, interface templates should be supported, and there should be - no restriction on the types of the parameters - `const` parameters, pointer - parameters, reference parameters, reference-to-`const` parameters, and etc - should all be allowed. - - gMock can also be used to mock a "loose" interface (i.e. the set of - operations a template class or template function expects its type argument - to support). This is useful for testing code that uses the - ["high-performance dependency injection"](https://engdoc.corp.google.com/eng/doc/tott/episodes/33.md) - technique. - -* **Precise specification of the intention:** gMock should enable a user to - precisely specify the intended behavior of a mock object, and how its - methods are expected to be called (in what order, with what arguments, etc). - In particular, it should not force the user to over-specify the problem - (which results in brittle tests that break when unrelated changes to the - code are made), or to under-specify the problem (which results in tests that - continue to pass when they shouldn't). - -* **Intuitive and declarative syntax:** A declarative syntax fosters thinking - at the right abstraction level, and makes the code readable and less - error-prone. Therefore gMock should provide intuitive and declarative syntax - for: - - 1. creating a mock class, and - 2. controlling the behavior of a mock object. When the two goals conflict, - the latter takes precedence, as it usually needs to be done many more - times than the former. - -* **Extensible:** No framework can be expected to cover all users' needs. - Therefore, gMock shouldn't tie the users to whatever it provides. Instead, a - user should be able to easily extend the framework to accomplish more - advanced tasks. - -* **Helpful error messages:** Bad error messages are a sure-fire way to - frustrate the users and drive them away. Therefore, gMock should generate - clear and sensible messages - - 1. when the code fails to compile - this can be hard as lots of templates - have to be used in the implementation, but we should try our best; and - 2. when a user-supplied expectation fails. This also applies to - user-defined extensions, given that the user has done a good job - implementing the extensions. - -* **Easy to learn:** We want gMock to make people's life easier, not harder. - It defeats our purpose if the framework is complex and difficult to learn. - -* **Easily automatable:** The design of gMock should make the process of - creating a mock class from an interface fairly mechanical, and thus doable - by the automated - [mock class generator](https://wiki.corp.google.com/twiki/bin/view/Main/MockClassGeneratorDev). - -* **Working in Google's environment:** While we may be interested in open - sourcing gMock later, our primary goal is to serve Google. Therefore gMock - must work well in our environment. In particular, it must not use - exceptions, and should work well with - [gUnit](https://wiki.corp.google.com/twiki/bin/view/Main/GUnitGuide). - -### Non-goals - -* **Mocking non-virtual methods:** gMock is a source-level tool that works - with standard compilers and linkers. It doesn't attempt to swap the object - code of a mock class and that of a real class on-the-fly. Therefore, only - virtual methods and template arguments can be mocked by gMock. -* **Supporting arbitrary number of parameters:** Due to limitations of the C++ - language, there will be a practical limit on the number of parameters a mock - function can have. Support for more parameters can be added as needed. -* **Supporting non-Linux platforms:** The initial implementation may not run - on Windows or Mac OS. We have limited resources and need to make sure that - Linux users are served first. However, we'll try to avoid doing things that - will make porting gMock to non-Linux platforms difficult. -* **Special support for particular projects:** gMock is a generic framework - that makes mocking easy for *all* Google C++ projects. It should not contain - logic that's useful only to a small number of projects. - -## Background - -### Terminology - -Different people often use "mock" to mean different things. This document -borrows the terminology popularized by -<a href="http://www.martinfowler.com/articles/mocksArentStubs.html">Martin -Fowler</a>: - -* **Dummy** objects are passed around but never actually used. Usually they - are just used to fill parameter lists. -* **Fake** objects actually have working implementations, but usually take - some shortcut (perhaps to make the operations less expensive), which makes - them not suitable for production. -* **Stubs** provide canned answers to calls made during the test, usually not - responding at all to anything outside what's programmed in for the test. -* **Mocks** are objects pre-programmed with expectations which form a - specification of the calls they are expected to receive. - -### Fakes vs Mocks - -Many people are not clear about the difference between a fake and a mock, and -use the terms interchangeably. However, to understand why we need gMock and what -it will deliver, it's crucial to distinguish the two. - -Compared with a fake, a mock object is "dumb" and usually doesn't have a working -implementation. However, it allows the user to control its behavior and set -expectations on the calls it will receive. For example, you can tell a mock -object that its `Foo()` method will be called twice with an argument that's -greater than 10, and it should return 12 and 14 respectively. - -It may seem that mocks are not very useful compared to fakes, but the Java -community has shown this perception to be wrong. The ability to control a mock -object's behavior and specify the expected interaction between it and the code -under test makes it far more flexible and useful than a fake in designing and -testing a software system. - -While fake classes have to be crafted with domain knowledge, mock classes can -actually be created mechanically - with suitable support from a framework. In -more dynamic languages like Java, C#, and Python, there are tools that create -mock objects on the fly without any user intervention. In C++, this cannot be -done within the language itself. However, a framework can make the task much -easier for a user, and the -[mock class generator](https://wiki.corp.google.com/twiki/bin/view/Main/MockClassGeneratorDev) -will make the process automated to a large extent. - -### C++ Mocking at Google - -To our knowledge, no tool or library is used at Google to facilitate the -creation of mock classes. As a result, people have been writing mock classes -manually. Such classes are typically tedious to create, and lack functionalities -for effective mocking. As a result, people are often frustrated and decided to -avoid mock classes. - -As a rough estimate, as of 3/15/2007, the number of existing C++ mock classes in -our source tree is: - -```shell -$ gsearch -f="\.(h|cc|cpp)$" -a -c "^\s*class\s+(Mock\w*|\w+Mock)\s*[:{]" -748 -``` - -while the number of all C++ classes is: - -```shell -$ gsearch -f="\.(h|cc|cpp)$" -a -c "^\s*class\s+\w+\s*[:{]" -188488 -``` - -Roughly 1 out of every 250 C++ classes has a corresponding mock class. Clearly -this is not enough. - -### Situation outside Google - -The situation of using C++ mocks outside of Google is not a lot brighter either. -Although there is an open-source framework -([mockpp](http://mockpp.sourceforge.net/)) for writing mock classes, it is -overly complex and has limited functionalities. As a result, it doesn't have a -large following. - -### Existing Mock Frameworks - -A good mock framework takes years of hard work and actual use in the field to -mature. Therefore, it pays hugely to learn from existing mock frameworks: what -they can and cannot do, why they are the way they are, how they have evolved, -what lessons their creators have learned, and what they intend to do next, etc. - -We studied some well-known mock frameworks for Java -([Mock Objects](http://www.mockobjects.com), -[EasyMock](http://www.easymock.org), [jMock 1](http://www.jmock.org), and -[jMock 2](http://cvs.jmock.codehaus.org/browse/~raw,r=1.3/jmock/website/content/cheat-sheet.html)) -and for C++ ([mockpp](http://mockpp.sourceforge.net/)). Our conclusion is: - -* Mock Objects is the most primitive of the four. It provides some basic - constructs for a user to set expected arguments and return values, but not - much beyond that. -* EasyMock makes the simple case very easy, but isn't flexible enough to - handle more advanced usage well. Often the users are forced to either - over-specify or under-specify their intention, resulting in brittle or - imprecise tests. -* jMock 1 and 2 share the same design philosophy, but have incompatible - syntaxes. They allow a user to precisely specify the intention of the test - in most cases, and can be easily extended by the user to handle more complex - situations. -* mockpp is a mixed bag of constructs from the above three. It doesn't have a - coherent design philosophy, and doesn't address C++'s specific requirements - well. It is more complex, redundant, and difficult to learn and use than we - would like. - -### Our Plan - -We believe that jMock is the most interesting and promising of the four. Its -creators have been aggressively experimenting with new ideas and designs, and -have produced many iterations before the current form. They have also documented -their experience and lessons in developing jMock in -[two](http://www.jmock.org/oopsla2004.pdf) -[papers](http://mockobjects.com/files/evolving_an_edsl.ooplsa2006.pdf), which -contain many valuable insights. - -Therefore, the design of gMock is heavily influenced by jMock. Many constructs -will be directly ported from jMock. Meanwhile, we'll revisit various design -decisions in C++'s context to make sure that we take advantages of C++ strengths -and avoid its weaknesses. We will also address some challenges that are unique -to C++. - -## Overview - -### Why a Framework - -Mock objects serve two distinct purposes in designing and testing a software -system: - -1. They implement the same interfaces as the real classes and provide canned - responses, allowing code that uses them to compile and run; and -2. They can verify that the actual interaction between them and the code under - test matches what the user expects (for example, the right functions are - called, in the right order, with the right arguments, etc). - -Without a framework, a user could manually implement mock functions to return -answers that are either pre-defined or computed using simplified logic. To -verify that the interaction that actually happens matches the expectation, a -user would typically let the mock functions record the interaction in some way, -and inspect the record in the end. This poor man's approach leaves several -things to be desired: - -1. Writing a mock class manually is not easy, and often viewed as a burden to - be avoided. -2. Different tests use a mock class in different ways. Therefore, it is often - impractical to provide a working fake implementation that is useful for all - tests. -3. Describing what the interaction should be by inspecting what really has - happened is round-about and unnatural. It obscure the intention of the test - author, and results in tests that are hard to read and understand. -4. It is often too late to check how the interaction went after it has - finished. Much better is to report a failure at the exact moment an - expectation is violated. This gives the user a chance to check the context - of the failure (the stack trace, the variables, etc) before important - information is lost. - -The purpose of gMock is to address the above problems. In particular, it will: - -1. make the task of writing a mock class much easier by hiding the low-level - mechanism from the user; -1. let the user of a mock class, rather than its creator, specify the intended - responses; -1. let the user specify the intended interaction in a clear and direct syntax; - and -1. catch violations to the specification as soon as they arise. - -### gMock's Expressiveness - -The Java community's years of experience using mocks shows that a mock framework -should enable a user to directly specify the following properties of the -interaction between a mock object and its surrounding code: - -* How many times will a function be called? -* What arguments will be used? -* In what order will the calls be made? -* What should the functions return? -* What side effects (if any) should the calls incur? - -Also, it's important to be able to loosen the constraints when necessary to -prevent brittle tests. For example, - -* If the test doesn't care about how many times a function will be called, the - test writer should be able to make that clear; -* If the exact value of an argument doesn't matter, the user should be able to - say so; -* If only a subset of the calls need to happen in a strict order, the user - should be allowed to specify a partial order. - -### Architecture of gMock - -gMock is a C++ library that will be linked into a user's test code. It consists -of the following components (the syntax used in the code samples is -*tentative*): - -1. **Function mockers:** A family of template classes will be provided for the - user to mock functions with different arities. For example, a field of type - - ``` - FunctionMocker<int(bool, const string&)> - ``` - - will be used to mock a function with signature - - ``` - virtual int Foo(bool, const string&); - ``` - -1. **Specification builder:** This provides a syntax for the user to specify - the expected arguments and responses of a mock function. For example, to say - that `Foo()` will be called exactly twice with arguments `true` and a string - that contains `"hello"`, and will return 10 and 12 respectively, the user - can write: - - ``` - EXPECT_CALL(mock_object, Foo(Eq(true), HasSubstring("hello")) - .Times(2) - .WillOnce(Return(10)) - .WillOnce(Return(12)) - ``` - -1. **Cardinalities, matchers, and actions:** A collection of pre-defined - *cardinalities* (e.g. `2`), argument *matchers* (e.g. `Eq()` and - `HasSubstring()`), and stub *actions* (e.g. `Return()`) will enable the user - to precisely specify the intended interaction in most cases. When this set - is inadequate, the user can easily define new cardinalities, matchers, and - actions. - -1. **Specification interpreter:** An underlying interpreter will verify that - the actual calls made to the mock object conform to the user's expectations. - -gMock helps a user in two kinds of activities: *writing* mock classes and -*using* them in tests. When writing a mock class, a user employs the function -mockers (#1); when using a mock class, the user relies on #2 and #3 to specify -the expected interaction between the mock object and the code under test. As the -test runs and the mock functions are invoked, the specification interpreter (#4) -verifies that the actual interaction matches the expectation, and fails the test -when the two don't match. - -## Detailed Design - -### Implementing a Mock - -This section explains how a user would implement a mock class using gMock. The -final syntax may be slightly different to what's presented here, but the overall -idea should remain the same. - -The goal of the design is to allow mocking functions that take 0 or more -arguments, functions that are overloaded on the number/types of parameters, -const methods, and methods that are overloaded on the const-ness of this object. - -#### Using macros - -The easiest way to define a mock class is to use the `MOCK_METHOD` macro. -Specifically, to mock an interface - -```cpp -class FooInterface { - ... - virtual R Method(A1 a1, A2 a2, ..., Am am) = 0; - virtual S ConstMethod(B1 b1, B2 b2, ..., Bn bn) = 0; -}; -``` - -one would simply write - -```cpp -class MockFoo : public FooInterface { - ... - MOCK_METHOD(R, Method, (A1 a1, A2 a2, ..., Am am), (override)); - MOCK_METHOD(S, ConstMethod, (B1 b1, B2 b2, ..., Bn bn), (const, override)); -}; -``` - -#### Using no macro - -The user can also choose to implement a mock class without using the macros. - -For each function to be mocked that is not overloaded, the user should define a -**function mocker** member variable and implement the function by forwarding the -call to the function mocker, which knows how to respond to the given arguments. - -A user specifies the mock function's default behavior and expectations on it by -calling the *mock spec function* in an `ON_CALL()` or `EXPECT_CALL()` statement. - -Now let's see the concrete syntax. To mock a function that takes no argument: - -```cpp -class AbcInterface { - ... - virtual R Foo() = 0; -}; -``` - -a user would write: - -```cpp -class MockAbc : public AbcInterface { - ... - // Mock Foo(). Implements AbcInterface::Foo(). - virtual R Foo() { return gmock_Foo.Invoke(); } - - FunctionMocker<R()> gmock_Foo; -}; -``` - -To mock a function that takes some arguments: - -```cpp - virtual R Bar(A1 a1, A2 a2); -``` - -a user would write: - -```cpp - virtual R Bar(A1 a1, A2 a2) { return gmock_Bar.Invoke(a1, a2); } - - FunctionMocker<R(A1, A2)> gmock_Bar; -``` - -To mock a `const` method: - -```cpp - virtual R Baz(A1 a1) const; -``` - -a user would write: - -```cpp - virtual R Baz(A1 a1) const { return gmock_Baz.Invoke(a1); } - - mutable FunctionMocker<R(A1)> gmock_Baz; -``` - -Mocking overloaded functions is a little bit more involved. For each overloaded -version, the user needs to define an overloaded mock controller function, e.g. - -```cpp - virtual R Bar(A a) { return gmock_Bar_1.Invoke(a); } - MockSpec<R(A)>& gmock_Bar(Matcher<A> a) { - return gmock_Bar_1.With(a); - } - - virtual R Bar(B b, C c) { return gmock_Bar_2.Invoke(b, c); } - MockSpec<R(B, C)>& gmock_Bar(Matcher<B> b, Matcher<C> c) { - return gmock_Bar_2.With(b, c); - } - private: - FunctionMocker<R(A)> gmock_Bar_1; - FunctionMocker<R(B, C)> gmock_Bar_2; -``` - -If a method is overloaded on the const-ness of this object, the user can -distinguish between the two overloaded versions by using a const- vs non-const- -reference to the mock object. The `Const()` function provided by gMock can be -used to get a const reference to an object conveniently: - -```cpp -template <typename T> -inline const T& Const(const T& x) { return x; } -``` - -### Syntax for Setting Default Actions and Expectations - -For each mock function, there are two interesting properties for a user to -specify: - -1. the **default action**: what the function should do by default when invoked, - and -2. the **expectations**: how the function will be called in a particular test. - -While the default actions of a mock class usually don't change from test to -test, a user typically sets different expectations in different tests. - -The following syntax is proposed for setting the default action of and the -expectations on a mock function: - -```cpp -ON_CALL(mock-object, method(argument-matchers)) - .With(multi-argument-matcher) ? - .WillByDefault(action); -``` - -The `ON_CALL()` statement defines what a mock function should do when its -arguments match the given matchers (unless the user overrides the behavior in -`EXPECT_CALL()`). The `With()` clause is optional. The `WillByDefault()` clause -must appear exactly once. - -```cpp -EXPECT_CALL(mock-object, method(argument-matchers)) - .With(multi-argument-matcher) ? - .Times(cardinality) ? - .InSequence(sequences) * - .WillOnce(action) * - .WillRepeatedly(action) ? - .RetiresOnSaturation(); ? -``` - -The `EXPECT_CALL()` statement says that the mock function should be called the -given number of times (`cardinality`), in the order determined by the -`sequences`, and with arguments that satisfy the given `matchers`. When it is -called, it will perform the given `action`. In this statement, all clauses are -optional and you can repeat `WillOnce()` any number of times. When no action is -specified, the default action defined by `ON_CALL()` will be taken. - -For non-overloaded methods, '(argument-matchers)' may be omitted: - -```cpp -ON_CALL(mock-object, method) - .With(multi-argument-matcher) ? - .WillByDefault(action); - -EXPECT_CALL(mock-object, method) - .With(multi-argument-matcher) ? - …cardinality and actions… -``` - -This allows test writers to omit the parameter list and match any call to the -method. Doing so eases the burden on test maintainers when refactoring method -signatures. The 'With()' clause is still optional when the parameter list is -omitted. - -We make `ON_CALL()` and `EXPECT_CALL()` macros such that we can tell the mock -object the file name and line number of a rule, which can be used to produce -better error messages at run time. When running a test inside Emacs and an -expectation is violated, the user can jump to the expectation by hitting -`<return>` on the message. - -#### Argument Matchers - -An `argument-matcher` can be any of the following: - -```cpp -Void(), Eq(value), Ge(value), Gt(value), Le(value), Lt(value), Ne(value), -HasSubstring(string), SubstringOf(string), -Same(value), Anything(), Any<type>(), Not(argument-matcher), AnyOf(argument-matchers), AllOf(argument-matchers) -``` - -In addition, a user can define custom matchers by implementing the -`MatcherImplInterface<type>` interface (TBD). - -#### Multi-argument Matchers - -Matchers in the previous section match one argument at a time. Sometimes it's -necessary to check all arguments together. This is when multi-argument matchers -are needed: - -```cpp -Eq(), Ge(), Gt(), Le(), Lt(), Ne(), -HasSubstring(), SubstringOf(), -Same(), AnyThings(), Not(multi-argument-matcher), AnyOf(multi-argument-matchers), AllOf(multi-argument-matchers) -``` - -When there are multiple `WithArguments()` clauses in a rule, all of them have to -be satisfied for the rule to match a call. - -A user can define new multi-argument matchers by implementing the -`MatcherImplInterface<std::tuple<type1, ..., type_n> >` interface (TBD). - -#### Actions - -```cpp -Return(), Return(value), DoDefault(), Fail(string), -SetArgPointee<N>(value), DoAll(actions), ... -``` - -The version of `Return()` that takes no argument is for mocking `void`-returning -functions. The clauses are all statically typed, so a user won't be able to -mistakenly use `Return()` when the mocked function has a non-void return type, -or to use `Return(value)` when the function returns `void`. - -On consecutive calls that match a given expectation, actions specified in -multiple `WillOnce()` clauses in the expectation will be used in the order they -are presented. After all `WillOnce()` clauses have been exhausted, the action -specified by `WillRepeatedly()` will always be used. If there is no -`WillRepeatedly()`, the default action defined by `ON_CALL()` will be taken. - -When side effects need to be mocked (e.g. changing a field or a global variable, -calling a function of a class-typed argument, and so on), users can define a -custom action by implementing the `ActionImplInterface<return-type(type1, ..., -type-n)>` interface (TBD). - -#### Cardinalities - -A cardinality tells how many times a function is expected to be called. The -number doesn't have to be always exact, as we don't want to over-specify the -behavior and result in brittle tests. - -```cpp -integer, AtLeast(n), AtMost(n), Between(m, n), AnyNumber() -``` - -This set can be extended by the user implementing the `CardinalityImplInterface` -interface (TBD). - -If no cardinality is specified in an `EXPECT_CALL()` statement, gMock will infer -it this way: - -* If there are n `WillOnce()` clauses but no `WillRepeatedly()`, the - cardinality is n; -* If there are n `WillOnce()` clauses and a `WillRepeatedly()`, the - cardinality is `AtLeast(n)`. - -#### Sequences - -Often we want to specify the order in which mock functions are called. However, -we may not want to specify a total order as that may lead to flaky tests that -will be broken by unrelated changes. For this reason, gMock allows the user to -specify a partial order on the calls by organizing them into *sequences*. - -Basically, a sequence is a chain of expectations that have to happen in the -order they are defined. Sequences are identified by their names. For example, -the following defines a sequence named `"a"`, which contains two expectations -where the first has to happen before the second: - -```cpp - Sequence a; - - EXPECT_CALL(mock_foo, Func1(Anything())) - .Times(1) - .InSequence(a); - - EXPECT_CALL(mock_bar, Func2(Eq(2))) - .Times(3) - .InSequence(a); -``` - -Note that expectations in the same sequence don't have to be on the same object -or same function, as the above example shows. - -An expectation can belong to any number of sequences, in which case all order -constraints have to be honored. For convenience, we allow `InSequence()` to take -multiple sequences. In the following example, the first expectation must be -matched before the second and the third, but we don't care about the relative -order of the latter two: - -```cpp - Sequence a, b; - - EXPECT_CALL(mock_foo, Func1(Anything())) - .Times(1) - .InSequence(a, b); - - EXPECT_CALL(mock_bar, Func2(Eq(2))) - .Times(AnyNumber()) - .InSequence(a); - - EXPECT_CALL(mock_bar, Func2(Eq(5))) - .Times(AnyNumber()) - .InSequence(b); -``` - -For convenience, we allow an expectation to contain multiple `InSequence()` -clauses, in which case their arguments will be joined. For example, another way -to write the first expectation in the above example is: - -```cpp - EXPECT_CALL(mock_foo, Func1(Anything())) - .Times(1) - .InSequence(a) - .InSequence(b); -``` - -A common scenario is that the user wants all expectations to match in the strict -order they are defined. Instead of letting the user put `InSequence()` in every -expectation, we provide the following short-hand: - -```cpp - { - InSequence s; - - EXPECT_CALL(...)...; - EXPECT_CALL(...)...; - ... - } -``` - -In the above snippet, when the variable `s` is constructed, gMock will generate -a unique new sequence and automatically put each `EXPECT_CALL()` in the scope of -`s` into this sequence. The result is that this group of expectations must match -in the strict order. - -The user can also use an existing sequence like this: - -```cpp - Sequence a; - ... - { - InSequence s(a); - - EXPECT_CALL(...)...; - EXPECT_CALL(...)...; - ... - } -``` - -This can be useful if an existing sequence needs to be extended. - -#### Examples - -```cpp -EXPECT_CALL(mock_goat, Eat(Eq(5), Anything())) - .WillOnce(Return(false)); -``` - -The mock goat will be told to `Eat()` 5 of something exactly once; the method -should return `false`. - -```cpp -EXPECT_CALL(mock_goat, Drink(HasSubstring("milk"))) - .Times(1); -``` - -The mock goat will be told to `Drink()` something that contains milk once; the -method should perform its default action when invoked. - -```cpp -EXPECT_CALL(mock_elephant, Eat(Same(mock_goat))) - .Times(0); -``` - -The mock elephant should never be told to `Eat()` the poor mock goat, which -would be a terrible thing. - -```cpp -Sequence a; - -EXPECT_CALL(mock_elephant, Eat(Anything())) - .InSequence(a) - .WillOnce(Return(true)); - -EXPECT_CALL(mock_elephant, Walk(Ge(5))) - .Times(AtLeast(1)) - .InSequence(a) - .WillOnce(Return(2)); -``` - -The mock elephant will be told to `Eat()` something; after that it will be told -to `Walk()` >= 5 meters at least once; the `Walk()` method should return 2 the -first time, and should do the default action in future calls. - -#### Syntax Checking - -We will use a combination of compile-time and run-time checks to catch syntax -errors. In particular, the spelling and types of the individual clauses will -(obviously) be done by the C++ compiler, while we'll enforce the order and -counts of the clauses via run-time checks. - -Please note that technically it is possible to do the latter checks at compile -time too, and that is the approach of jMock and Mockpp. For the designer of an -embedded domain-specific language (EDSL), it is appealing to leverage the -compiler of the hosting language (C++ in this case) to parse code in the EDSL -and catch errors in it as much as possible. It is also an interesting exercise -in pushing the envelope of EDSL implementation techniques. - -However, while we initially wanted to go with jMock's approach, we now think -it's better to defer such checks to run time. The reasons are: - -1. Doing the checks at run time *significantly* reduces the number of template - classes and simplifies the implementation. This is not only a benefit for - the author and maintainer of gMock, but also makes it much easier for a user - to learn gMock. New and existing users will have to read the gMock header - files from time to time, so it's important to keep the public interface - small. As an example of what happens when the API is not kept small, try to - read the header files of Mockpp - you will find a plethora of template - classes that reference each other, and it's very difficult to tell what - different roles they play. -1. The jMock approach enables the IDE to automatically suggest the next clause - when a user is writing an expectation statement and thus makes it trivial to - write syntactically correct expectations. Unfortunately, such benefit is - merely theoretic for most C++ users, as C++ is such a complex language that - most IDEs do a poor job at understanding the user's source code and - suggesting auto-completion. -1. C++ templates generate horrible, horrible compiler errors that often baffle - even experienced programmers. By enforcing the syntax at compile time, we - subject gMock's users to the mercy of the C++ compiler, which will generate - lengthy and cryptic errors when a user makes a small mistake in the syntax. - It would be much better for us to generate the errors at run time, as we can - control the messages and choose plain and clear language that guides the - user to fix the problem. -1. The default action and expectation statements in gMock are *declarative*, - and typically each of them will be executed once during the test (not to be - confused with a rule *matching* an invocation multiple times). Therefore - there should be little concern that a syntax error is not caught because the - statement is never actually executed. - -### Formal Semantics - -The previous section presented the syntax and informally explained the meanings -of various clauses. To avoid ambiguities and make sure we all have the same -understanding on the meaning of a complete test using mock objects, we need to -define the semantics of gMock more strictly. - -For an expectation rule to match an actual invocation, three types of -constraints have to be satisfied at the same time: - -1. the order constraints (does the call occur in the right order?), -2. the cardinality constraints (can the rule accept more invocations?), and -3. the argument constraints (do all arguments satisfy their matchers?). - -As the designer of gMock, we need to decide in which order these constraints -should be applied and how to resolve ambiguities. Our goal is to choose a -semantics that is easy to understand and allows the user to easily express -properties useful for writing tests. - -Given that gMock borrows heavily from jMock, naturally one would try to adopt -jMock's semantics. I couldn't find a documentation on that unfortunately. The -following semantics is based on my reverse-engineering jMock and what I think is -reasonable. It differs from the jMock semantics in several important regards. -The exact differences and the rationale behind our decision can be found on the -c-mock-dev [archive](https://g.corp.google.com/group/c-mock-dev-archive) and are -not repeated here. - -The proposed semantics can be summarized by two simple principles: - -1. **The orders are sacred**: under no circumstance can an expectation in a - sequence to match before all expectations that appear earlier in the same - sequence have been satisfied; and -2. **Earlier rules take precedence:** when multiple rules can match an - invocation without violating the order constraints, the one defined the - earliest wins. - -To define the semantics formally, we will use the following terminology: - -* An `ON_CALL()` statement defines a **default action**. -* An `EXPECT_CALL()` statement defines an **expectation**. -* An expectation is **active** iff it still can be used to match invocations. - Otherwise it is **retired**. Initially, all expectations are active. -* An expectation X is an **immediate pre-requisite** of another expectation Y - iff there exists a sequence S where X and Y are both in S, X is defined - before Y, and there is no expectation in S between X and Y. -* An expectation X is a **pre-requisite** of another expectation Y iff there - exists a list X[0] = X, X[1], ..., X[n] = Y, where X[i] is an immediate - pre-requisite of X[i+1] for all i. -* An expectation (or its cardinality constraint) is said to be **satisfied** - iff it has reached its minimum number of allowed invocations. -* An expectation (or its cardinality constraint) is said to be **saturated** - iff it has reached its maximum number of allowed invocations. A saturated - expectation by definition must be satisfied, but not vice versa. - -After the user has set the default action and the expectations, when a mock -function is called, the following algorithm (in pseudo code) will be used to -find the matching expectation and the matching action: - -```cpp -void TryToDoDefault(FunctionMocker& m, const Arguments& args) { - if (m has a default action for arguments args) { - perform the default action; - } else { - raise error("No action is specified."); - } -} - -void OnInvocation(FunctionMocker& m, const Arguments& args) { - for_each (active expectation e on function m in the order - the expectations are defined) { - if (all pre-requisites of e are satisfied && - args match e's argument matchers) { - // We found a match! - - if (e.is_saturated) - raise error("Invocation upper bound exceeded."); - - e.invocation_count++; - retire all prerequisites of e; - - if (e.retires_on_saturation && e.is_saturated) - e.is_active = false; - - if (e has more action left) { - a = e.get_next_action(); - perform a; - } else { - TryToDoDefault(m, args); - } - return; - } - } - - TryToDoDefault(m, args); -} -``` - -To find the default action for the given arguments, we look through all -`ON_CALL()` rules for the mock function, and pick the first one where all -argument matchers are satisfied, if any. - -Since C++ exceptions are disabled in `google3`, **we will abort the current -process when gMock raises an error**. We cannot just return from the current -function like what gUnit does, as the mock functions will be called from the -production code under test, and we don't have the luxury to change the -production code at each call site to propagate the error. This is unfortunate, -but I don't see a better solution without enabling exceptions. - -The real implementation will be more sophisticated in order to get a decent -performance (e.g. we'll memoize and use other tricks), but the end result must -match the above reference implementation. - -**Note:** If you carefully inspect the algorithm, you should convince yourself -that an expectation whose cardinality is `0` has no effect whatsoever, as it is -always satisfied and saturated. This means that you can write such an -expectation, but it won't affect your test in any way. Indeed, this is jMock's -behavior, and jMock's documentation suggests to use `Never()` (jMock's -equivalent of the `0` cardinality) for documentation purpose only. - -This bothers me as it contradicts with what one would naturally expect. When I -see - -```cpp - EXPECT_CALL(mock_foo, Bar(Eq(5))) - .Times(0); -``` - -I would think that it will be an error if `mock_foo.Bar(5)` is ever called, and -gMock will catch this error at run time. However, jMock tells me that it will -not try to enforce this, and I should treat the statement as if it doesn't -exist. - -I propose to give `Times(0)` a semantics that I think is more intuitive. Namely, -we should treat - -```cpp - EXPECT_CALL(mock-object, method(argument-matchers)) - .WithArguments(multi-argument-matcher) - .Times(0) - .InSequence(sequences); -``` - -as if it were - -```cpp - EXPECT_CALL(mock-object, method(argument-matchers)) - .WithArguments(multi-argument-matcher) - .Times(AnyNumber()) - .InSequence(sequences) - .WillOnce(Fail("Unexpected call.")); -``` - -I don't like making this a special case, but the other choice seems worse. - -**Note:** If a call doesn't match any explicitly written `EXPECT_CALL()` -statement, gMock will perform the default action (as long as it exists) instead -of raising an "unexpected call" error. If you want to assert that a function -should never be called, you must explicitly write an `EXPECT_CALL()` with a `0` -cardinality. This design is picked to allow modular tests: - -An interface may contain many methods. Typically, each test will be interested -in only a small number of them, as we favor small and focused tests. Such a test -shouldn't start to fail when the code under test is modified to call functions -not interesting to the test. If no `EXPECT_CALL()` were to mean "no call is -allowed", we would have to say - -```cpp - EXPECT_CALL(mock_foo, UninterestingMethod(Anything())) - .Times(AnyNumber()); -``` - -for **every** method we do **not** care about. It can be very tedious. Worse, -when we add methods to the interface or remove methods from it, we have to -update every existing test. Clearly this isn't modular and won't scale. - -#### Examples - -If you are not interested in whether a function will be called or not, you just -don't say anything about it. If the function is called, its default action will -be performed. - -If you want to make sure that a function is never called, say it explicitly: - -```cpp - EXPECT_CALL(mock_foo, Bar).Times(0); - // or: - EXPECT_CALL(mock_foo, Bar(Anything())).Times(0); -``` - -If you expect certain calls to a function and want to ignore the rest, just -specify the calls you are explicitly expecting: - -```cpp - EXPECT_CALL(mock_foo, Bar(Eq(1))) - .WillOnce(Return(2)); - EXPECT_CALL(mock_foo, Bar(Eq(2))) - .Times(AtMost(5)) - .WillRepeatedly(Return(3)); -``` - -If you expect certain calls to a function and don't want to allow any other -calls to it, just add a `Times(0)` expectation **after** the normal -expectations: - -```cpp - EXPECT_CALL(mock_foo, Bar(Eq(1))) - .WillOnce(Return(2)); - EXPECT_CALL(mock_foo, Bar(Eq(2))) - .Times(AtMost(5)) - .WillRepeatedly(Return(3)); - - // Any call to mock_foo.Bar() that doesn't match the above rules - // will be an error. - EXPECT_CALL(mock_foo, Bar(Anything())) - .Times(0); -``` - -Here's one complete example: - -```cpp - ON_CALL(mock_foo, Bar(Anything())) - .WillByDefault(Return(1)); - - Sequence x; - - EXPECT_CALL(mock_foo, Bar(Ne('a'))) // Expectation #1 - .InSequence(x) - .WillOnce(Return(2)) - .WillRepeatedly(Return(3)); - - EXPECT_CALL(mock_foo, Bar(Anything())) // Expectation #2 - .Times(AnyNumber()) - .InSequence(x); - - mock_foo.Bar('b'); // Matches expectation #1; returns 2. - mock_foo.Bar('c'); // Matches expectation #1; returns 3. - mock_foo.Bar('b'); // Matches expectation #1; returns 3. - mock_foo.Bar('a'); // Matches expectation #2; returns 1. - - // Now that expectation #2 has been used, expectation #1 becomes - // inactive (remember that the order is sacred), even though it's not - // yet saturated. - - mock_foo.Bar('b'); // Matches expectation #2, returns 1. -``` - -Another one: - -```cpp - Sequence a, b; - - EXPECT_CALL(mock_foo, Func1(Void())) // #1 - .Times(1) - .InSequence(a); - - EXPECT_CALL(mock_bar, Func2(Anything()) // #2 - .Times(AtLeast(1)) - .InSequence( b); - - EXPECT_CALL(mock_foo, Func3(Eq(0))) // #3 - .Times(AtMost(2)) - .InSequence(a, b); - - EXPECT_CALL(mock_foo, Func3(Anything())) // #4 - .InSequence(a); - - // The order constraints can be illustrated as - // - // #1 < #3 < #4 - // #2 < #3 - - mock_foo.Func1(); // Matches #1 - // Now #1 is saturated but not retired. - // If Func1() is called again here, it will be an upper-bound error. - - // It would be an error to call mock_foo.Func3(0) here, as #2 is its - // pre-requisite and hasn't been satisfied. - - mock_bar.Func2(1); // Matches #2, which is now satisfied. - - mock_foo.Func3(1); - // Matches #4. This causes all of #4's remaining pre-requisites (#2 - // and #3) to become inactive. Note that #3 is trivially satisfied - // as that AtMost(2) doesn't require it to match any invocation. -``` - -Yet another one: - -```cpp -EXPECT_CALL(mock_foo, Func(Eq(1))) // #1 - .WillOnce(Return(2)) - .RetiresOnSaturation(); - -EXPECT_CALL(mock_foo, Func(Anything())) // #2 - .WillOnce(Return(3)); - -mock_foo.Func(1); // Matches #1. -// Now #1 is satisfied, saturated, and retired. - -mock_foo.Func(1); // Matches #2. -// Since #1 is retired now, it doesn't participate in matching function -// calls. Otherwise this would cause an upper-bound-exceeded failure. -``` - -### Verifying that All Expectations Are Satisfied - -During a test, gMock will verify that each invocation to a mock function matches -one of the expectation rules. However, at the end of a test, we will want to -verify that *all expectations for the mock function have been satisfied*. This -is done by the destructor of the `FunctionMocker<...>` class: - -### Life of a Mock - -Now let's put the pieces together and see the complete process of using mock -objects in a test. Typically, the user should do it in the following order: - -* **C:** *Constructs* the mock objects; -* **B:** Set their default **behaviors** using `ON_CALL()`; -* **E:** Set **expectations** on them using `EXPECT_CALL()`; -* **I:** Exercise the production code, which will **invoke** methods of the - mock objects; -* **D:** *Destructs* the mock objects, which will cause gMock to verify that - all expectations are satisfied. - -Usually, the user can do step 1 and 2 during the set-up phase of the test, step -3 and 4 in the test function body, and step 5 in the tear-down phase. - -If the user performs a step out of sequence (e.g. an `EXPECT_CALL()` is -encountered after the mock function is already been called by the test and -before `Verify()` is called), the behavior is **undefined**. gMock will try to -print a friendly error message, but doesn't guarantee to catch all possible -violations, and the initial version may not implement this error check at all. - -Valid sequences of using a mock object can be described using the regular -expression - -```none -CB*E*I*D -``` - -### Typing of Argument Matchers - -Argument matchers in gMock are statically typed. If we don't provide automatic -conversion between matchers of "compatible" types, the user experience will be -rather unpleasant. Covariance and contravariance are two common schemes for -imposing a sub-typing relation between types. Our observation is that neither -works for matchers in general, and gMock must leave the decision to individual -matcher authors. - -#### Background: How Argument Matchers Work - -In gMock, argument matchers are used to determine if the actual arguments in a -function invocation match the test writer's expectation. Conceptually, a matcher -for arguments of type `T` implements the following interface: - -```cpp -class Matcher<T> { - virtual bool Matches(T x) = 0; -}; -``` - -For a method with argument type `T`: - -```cpp -virtual void Func(T x); -``` - -its mock will be declared as something like (the actual declaration will be more -complicated but the idea remains the same): - -```cpp -void Func(Matcher<T>* x); -``` - -When the mock `Func()` is invoked with an argument value `v`, which has type -`T`, `Matches(v)` will be called to determine if it's a match. - -#### Need for Sub-typing - -A straightforward way to mock a method with parameter types `T1`, `T2`, ..., and -`Tn` is to use a list of matchers of type `Matcher<T1>`, `Matcher<T2>`, ..., and -`Matcher<Tn>`. However, this simplistic approach has a usability problem. -Suppose we have a series of functions and their mocks: - -```cpp -void Func1(char a); -void Func1(Matcher<char>* a); - -void Func2(const char a); -void Func2(Matcher<const char>* a); - -void Func3(char& a); -void Func3(Matcher<char&>* a); - -void Func4(const char& a); -void Func4(Matcher<const char&>* a); - -void Func5(char* a); -void Func5(Matcher<char*>* a); - -void Func6(const char* a); -void Func6(Matcher<const char*>* a); -``` - -(note that `Func2()` has a `const` parameter. Since argument matchers are not -allowed to modify the arguments in any case, technically we could use a -`Matcher<char>` in the mock of `Func2()`. However, we want to make sure that a -user can define the mock using a `Matcher<const char>` too, as this makes the -task of the mock class generator easier.) and some simple, pre-defined matcher -factories: - -```cpp -// Matches if the argument equals the given value x. -Matcher<T>* Eq(T x); - -// Matches if the argument has the same identify as the -// given object x. -Matcher<T&>* Same(T& x); -``` - -then a user might be surprised when trying to use these mocks: - -```cpp - Func1('a'); // Invokes the real method. This works fine. - Func1(Eq('a')); // Invokes the mock method. This works fine too. - - Func2('a'); // Invokes the real method. This works fine. - Func2(Eq('a')); // Compiler ERROR - surprise!!! Why can't I say that - // the argument, which is a const char, should be equal - // to 'a'? - - char a = 'a'; - Func3(a); // Invokes the real method. This works fine. - Func3(Same(a)); // Fine. The argument should reference the variable a. - Func3(Eq('a')); // Compiler ERROR - surprise!!! Why can't I say that - // the argument, which is a char&, should have a value - // 'a', which is a char? - - const char b = 'b'; - Func4(b); // Fine. - Func4(Same(b)); // Fine. The argument should reference the variable b. - Func4(Eq(b)); // Compiler ERROR - surprise!!! Why can't I say that - // the argument, which is a const char&, should have - // a value equal to b, which is a const char? - Func4(Same(a)); // Compiler ERROR - surprise!!! Why can't I say that - // the argument, which is a const char&, should reference - // a, which is a char? - - char* p = NULL; - Func5(p); // Fine. - Func5(Eq(p)); // Fine. - - Func6("a"); // Fine. - Func6(Eq("a")); // Fine. - Func6(Eq(p)); // Compiler ERROR - surprise!!! Why can't I say that - // the argument, which is a const char*, should point - // to where p, which is a char*, points to? -``` - -(In Java, this issue isn't nearly as severe, as Java has neither reference nor -`const`. Lucky them.) - -The compiler errors can be worked around using explicit template instantiating -in most cases, but require more dirty hacks in some others: - -```cpp - // The following works: - Func2(Eq<const char>('a')); - Func4(Eq<const char&>(b)); - Func4(Same<const char>(a)); - Func6(Eq<const char*>(p)); - - // but this doesn't: - Func3(Eq<char&>('a')); // Compiler ERROR! - - // You have to use a temporary variable, and pray that it's not - // accidentally changed before the actual invocation occurs. - // No, you cannot make the temporary variable const - that won't - // compile. - char temp = 'a'; - Func3(Eq<char&>(temp)); -``` - -Having to use these tricks all the time is a big bummer and makes the tests -harder to read. The author of Mockpp either chose to ignore this problem, or -wasn't aware of it, but I don't think that's a good solution. - -To give the user a satisfying experience, I believe we should provide automatic -conversions between matchers of "compatible" types when it makes sense (i.e. we -should establish a sub-typing relation between matcher types). The challenges -are: - -1. Deciding when "it makes sense", -1. Making sure the conversions are neither too restricted nor too liberal, -1. Making it possible for the user to understand the compiler errors when - automatic conversions cannot be done, -1. Making the rules easy to learn and remember, and -1. Implementing it. - -#### Covariant or Contravariant? - -We already know that making the matchers **invariant** (i.e. no auto-conversion -between matcher types) doesn't work, but what about **covariant** (`Matcher<A>` -can be used as `Matcher<B>` as long as `A` can be used as `B`) or -**contravariant** (`Matcher<A>` can be used as `Matcher<B>` as long as `B` can -be used as `A`)? Would one of them work? - -It's easy to see that covariance doesn't work in general, as it requires a -matcher expecting a sub-type value to inspect a super-type value. What if the -matcher needs to look at a field that's only present in the sub-type? - -On the surface level, it seems that contravariance is what we need: if type `B` -can be implicitly converted to type `A`, then given an argument of type `B`, we -can convert it to type `A` and then ask a `Matcher<A>` whether the converted -value matches. This means that we can use a `Matcher<A>` in place of a -`Matcher<B>`. - -For example, given a class hierarchy and some (real and mock) functions that use -the classes: - -```cpp -class Father { ... }; - -class Son : public Father { - public: - ... - // New method not present in Father: - virtual bool PropertyFoo() const; -}; - -class Grandson : public Son { ... }; - -void InviteFather(Father* obj); -void InviteFather(Matcher<Father*>* m); - -void InviteGrandson(Grandson* obj); -void InviteGrandson(Matcher<Grandson*>* m); -``` - -we can expect to write the following: - -```cpp -// Matches if the argument's PropertyFoo() method returns true. -Matcher<Son*>* HasFoo() { ... } - -// The compiler should reject this as a Father object doesn't have -// the PropertyFoo() method: -// -// InviteFather(HasFoo()); - -// This should work, as a Grandson object is also a Son object and -// has the PropertyFoo() method. -InviteGrandson(HasFoo()); -``` - -In the latter case, the actual argument (of type `Grandson*`) will be implicitly -converted to a `Son*` and then passed to the matcher. - -However, things are not always so simple. Take the example of the equality -matcher, `Func5()`, and `Func6()` we saw earlier: - -```cpp -// Matches if the argument equals the given value x. -Matcher<T>* Eq(T x); - -void Func5(char* a); -void Func5(Matcher<char*>* a); - -void Func6(const char* a); -void Func6(Matcher<const char*>* a); -``` - -By making matchers contravariant, we have - -```cpp - // Remember that a char* can be implicitly converted to a const char*. - - Func5(Eq("a")); // Compiles, but we DON'T want it to!!! The user is - // trying to say that the actual argument (a char*) - // can be "a", and we should catch this error. - - char* p = ...; - Func6(Eq(p)); // Still a compiler ERROR, as a const char* cannot be - // implicitly converted to a char*, which Eq(p) expects. -``` - -Clearly this isn't what we want. In fact, we want `Eq(value)` to be covariant: - -```cpp - char* p = ...; - - Func5(p); - Func5(Eq(p)); - // Func5("a"); // The compiler will reject this, - // Func5(Eq("a")); // and thus should reject this too. - - Func6("a"); - Func6(Eq("a")); - Func6(p); // The compiler accepts this, - Func6(Eq(p)); // and thus should accept this too. -``` - -In another example: - -```cpp -void InviteSon(Son* obj); -void InviteSon(Matcher<Son*> m); - -Father* father = ...; -Grandson* grandson = ...; - -InviteSon(grandson); // The compiler accepts this, -InviteSon(Eq(grandson)); // and thus should accept this too. - -// InviteSon(father); // The compiler will reject this, -// InviteSon(Eq(father)); // and thus should reject this too. -``` - -So, what was the problem? The key insight here is that *one size doesn't fit -all*. While some matchers should be contravariant (like `HasFoo()`), some should -be covariant (like `Eq(value)` and `Same(object)`). *The decision has to be left -to the individual matcher authors. gMock should not impose a global policy on -all the matchers.* - -#### Implementing Automatic Type Conversion - -In C++, you have several options if you want to make one class `A` act like -another class `B`: - -1. Derive `A` from `B`; -1. In class `B`, define a public single-parameter constructor `B::B(const A&)` - (don't make it `explicit`); -1. In class `A`, define a type-conversion operator for type `B`. - -Each of these approaches has its limitations: - -* #1 is most straightforward and requires the least amount of work. However, - it means that an `A` object will contain all the members of `B`. It may not - work for you if you want to be able to auto-convert `A` to multiple classes, - and it certainly won't work if you want to convert `A` to an infinite number - of other classes. -* #2 requires you to be able to edit the implementation of `B`. This is not - always possible, for example, when `B` is a class defined in a standard - library and you are a user of that library. It's a closed approach, meaning - that only the owner of `B` can decide which classes can be converted to `B`. -* #3 requires more work to implement typically, but doesn't have the problems - of #1 and #2. In particular, you can define a template type-conversion - operator to convert `A` to an infinite number of other classes of your - choice. - -Also, remember that the compiler will only automatically insert one level of -type conversion on your behalf. For example, if `A` can be implicitly converted -to `B`, which can be implicitly converted to `C`, and you have a function -expecting a `C`, you cannot give the function an `A` without explicit casting, -unless `A` can be implicitly converted to `C` too. - -gMock defines the `Matcher<T>` interface, which a user cannot modify. When -defining a polymorphic matcher (e.g. `Eq(value)`), a user needs to make it -behave like a (potentially infinite) number of matchers of different types. This -means that the last implementation technique should be used. - -### Comparison with Mockpp and jMock - -See GMockVsMockppAndJMock. - -## Project - -This design doc describes the project "[gMock](http://p?p=6164) - a framework -for writing C++ mock classes" in PDB. - -## Code Location - -This is a new project, so no existing file is expected to be touched. The -implementation is added in directory `//depot/google3/testing/base`. - -## Group Members - -ZhanyongWan : spending 60% of his time on this. - -## Caveats - -We considered existing solutions, but don't think they would work well enough -for Google. For details, please refer to MockppStudy. - -TODO: - -* Explain why we pick the EDSL-style syntax. - -## Documentation Plan - -In additional to this design doc, a user's guide, an FAQ, and a codelab will -also be written. - -## Testing Plan - -gMock will be thoroughly tested on Linux using gUnit. - -## Work Estimates - -* **Inspecting existing solutions:** The goal is to understand how other - people have approached this problem, what they did well, and what did - poorly. In addition to studying solutions for C++ (mockpp), we will also - study solutions for Java (jMock and EasyMock). **3 weeks.** -* **Initial design and prototyping:** Come up with a design tailored to C++'s - specifics and Google's unique requirements, taking into account lessons - learned from other solutions. **3 weeks.** -* **Soliciting feedback on the design:** Listen to `testing-technology`, - `testing-grouplet`, `c-users`, `c-mock-dev`, and `gunit-users`; revise the - design based on the feedback. **3 weeks.** -* **Initial implementation:** **6 weeks.** -* **Documentation:** Write the user's guide and a codelab. **3 weeks.** -* **Company-wide roll-out:** Implement a process for promoting and tracking - adoption. **1 week.** -* **Customer support, incremental improvements, and maintenance:** **On-going - effort.** - -## Potential Patents - -We'll know whether there will be patentable inventions when we have a more -concrete design and prototype. At that time, we should talk to Google's -[patent counsel](mailto:patents@google.com). - -## Things that Don't Apply - -### Security Considerations - -This is an internal library for writing (unit) tests, and will not be used in -production. Therefore there is no security concern. - -### Privacy Considerations - -gMock will not touch any user data. Therefore there is no concern about user -privacy. - -### Standards - -There is no existing standard in creating C++ mocks. - -### Logging Plan - -This is an internal library and will not handle any user request. Therefore -there is no plan for logging. - -### Monitoring Plan - -This is an internal library and will not run on our production servers. -Therefore no monitoring is required. - -### Internationalization Plan - -gMock is not visible to external users, so there is no plan to internationalize -it. - -### Billing Plan and Tax Plan - -gMock is an internal library and doesn't involve money, so there is no billing -plan or tax plan. - -### Launch Plans - -gMock will not launch externally as a Google property. However, we may later -decide to open source it. - -## References - -* [jMock 1 cheat sheet](https://wiki.corp.google.com/twiki/bin/view/Main/JMockOneCheatSheet) - - I compiled this from the downloaded jMock 1 source code. -* [jMock 1 JavaDoc](http://www.corp.google.com/~wan/jmock1/javadoc/) - I built - this locally. The one on http://jmock.org can be slow and may change. -* [jMock 2 cheat sheet](http://www.jmock.org/cheat-sheet.html) - as found on - http://jmock.org. -* [jMock 2 cheat sheet](https://wiki.corp.google.com/twiki/bin/view/Main/JMockTwoCheatSheet) - - I compiled this from the jMock 2 source code in CVS as of 3/21. -* [jMock 2 JavaDoc](http://www.corp.google.com/~wan/jmock2/javadoc) - I - generated this locally from the jMock 2 source code in CVS as of 3/21. No - official jMock 2 JavaDoc is available yet, as the library hasn't been - released. -* [mockpp cheat sheet](https://wiki.corp.google.com/twiki/bin/view/Main/MockppCheatSheet) - - I compiled this from the mockpp source code. -* [mockpp API docs](http://mockpp.sourceforge.net/api-doc/index.html) - - external. - -## Acknowledgments - -This design doc contains many ideas from PiotrKaminski. We'd also like to thank -the following people for contributing ideas to this project: - -JoeWalnes, CraigSilverstein, JeffreyYasskin, KeithRay, MikeBland. diff --git a/googlemock/docs/for_dummies.md b/googlemock/docs/for_dummies.md deleted file mode 100644 index 8ba164f..0000000 --- a/googlemock/docs/for_dummies.md +++ /dev/null @@ -1,702 +0,0 @@ -# gMock for Dummies {#GMockForDummies} - -<!-- GOOGLETEST_CM0013 DO NOT DELETE --> - -<!-- GOOGLETEST_CM0035 DO NOT DELETE --> - -## What Is gMock? - -When you write a prototype or test, often it's not feasible or wise to rely on -real objects entirely. A **mock object** implements the same interface as a real -object (so it can be used as one), but lets you specify at run time how it will -be used and what it should do (which methods will be called? in which order? how -many times? with what arguments? what will they return? etc). - -**Note:** It is easy to confuse the term *fake objects* with mock objects. Fakes -and mocks actually mean very different things in the Test-Driven Development -(TDD) community: - -* **Fake** objects have working implementations, but usually take some - shortcut (perhaps to make the operations less expensive), which makes them - not suitable for production. An in-memory file system would be an example of - a fake. -* **Mocks** are objects pre-programmed with *expectations*, which form a - specification of the calls they are expected to receive. - -If all this seems too abstract for you, don't worry - the most important thing -to remember is that a mock allows you to check the *interaction* between itself -and code that uses it. The difference between fakes and mocks shall become much -clearer once you start to use mocks. - -**gMock** is a library (sometimes we also call it a "framework" to make it sound -cool) for creating mock classes and using them. It does to C++ what -jMock/EasyMock does to Java (well, more or less). - -When using gMock, - -1. first, you use some simple macros to describe the interface you want to - mock, and they will expand to the implementation of your mock class; -2. next, you create some mock objects and specify its expectations and behavior - using an intuitive syntax; -3. then you exercise code that uses the mock objects. gMock will catch any - violation to the expectations as soon as it arises. - -## Why gMock? - -While mock objects help you remove unnecessary dependencies in tests and make -them fast and reliable, using mocks manually in C++ is *hard*: - -* Someone has to implement the mocks. The job is usually tedious and - error-prone. No wonder people go great distance to avoid it. -* The quality of those manually written mocks is a bit, uh, unpredictable. You - may see some really polished ones, but you may also see some that were - hacked up in a hurry and have all sorts of ad hoc restrictions. -* The knowledge you gained from using one mock doesn't transfer to the next - one. - -In contrast, Java and Python programmers have some fine mock frameworks (jMock, -EasyMock, [Mox](http://wtf/mox), etc), which automate the creation of mocks. As -a result, mocking is a proven effective technique and widely adopted practice in -those communities. Having the right tool absolutely makes the difference. - -gMock was built to help C++ programmers. It was inspired by jMock and EasyMock, -but designed with C++'s specifics in mind. It is your friend if any of the -following problems is bothering you: - -* You are stuck with a sub-optimal design and wish you had done more - prototyping before it was too late, but prototyping in C++ is by no means - "rapid". -* Your tests are slow as they depend on too many libraries or use expensive - resources (e.g. a database). -* Your tests are brittle as some resources they use are unreliable (e.g. the - network). -* You want to test how your code handles a failure (e.g. a file checksum - error), but it's not easy to cause one. -* You need to make sure that your module interacts with other modules in the - right way, but it's hard to observe the interaction; therefore you resort to - observing the side effects at the end of the action, but it's awkward at - best. -* You want to "mock out" your dependencies, except that they don't have mock - implementations yet; and, frankly, you aren't thrilled by some of those - hand-written mocks. - -We encourage you to use gMock as - -* a *design* tool, for it lets you experiment with your interface design early - and often. More iterations lead to better designs! -* a *testing* tool to cut your tests' outbound dependencies and probe the - interaction between your module and its collaborators. - -## Getting Started - -gMock is bundled with googletest. - -## A Case for Mock Turtles - -Let's look at an example. Suppose you are developing a graphics program that -relies on a [LOGO](http://en.wikipedia.org/wiki/Logo_programming_language)-like -API for drawing. How would you test that it does the right thing? Well, you can -run it and compare the screen with a golden screen snapshot, but let's admit it: -tests like this are expensive to run and fragile (What if you just upgraded to a -shiny new graphics card that has better anti-aliasing? Suddenly you have to -update all your golden images.). It would be too painful if all your tests are -like this. Fortunately, you learned about -[Dependency Injection](http://en.wikipedia.org/wiki/Dependency_injection) and know the right thing -to do: instead of having your application talk to the system API directly, wrap -the API in an interface (say, `Turtle`) and code to that interface: - -```cpp -class Turtle { - ... - virtual ~Turtle() {} - virtual void PenUp() = 0; - virtual void PenDown() = 0; - virtual void Forward(int distance) = 0; - virtual void Turn(int degrees) = 0; - virtual void GoTo(int x, int y) = 0; - virtual int GetX() const = 0; - virtual int GetY() const = 0; -}; -``` - -(Note that the destructor of `Turtle` **must** be virtual, as is the case for -**all** classes you intend to inherit from - otherwise the destructor of the -derived class will not be called when you delete an object through a base -pointer, and you'll get corrupted program states like memory leaks.) - -You can control whether the turtle's movement will leave a trace using `PenUp()` -and `PenDown()`, and control its movement using `Forward()`, `Turn()`, and -`GoTo()`. Finally, `GetX()` and `GetY()` tell you the current position of the -turtle. - -Your program will normally use a real implementation of this interface. In -tests, you can use a mock implementation instead. This allows you to easily -check what drawing primitives your program is calling, with what arguments, and -in which order. Tests written this way are much more robust (they won't break -because your new machine does anti-aliasing differently), easier to read and -maintain (the intent of a test is expressed in the code, not in some binary -images), and run *much, much faster*. - -## Writing the Mock Class - -If you are lucky, the mocks you need to use have already been implemented by -some nice people. If, however, you find yourself in the position to write a mock -class, relax - gMock turns this task into a fun game! (Well, almost.) - -### How to Define It - -Using the `Turtle` interface as example, here are the simple steps you need to -follow: - -* Derive a class `MockTurtle` from `Turtle`. -* Take a *virtual* function of `Turtle` (while it's possible to - [mock non-virtual methods using templates](cook_book.md#MockingNonVirtualMethods), - it's much more involved). -* In the `public:` section of the child class, write `MOCK_METHOD();` -* Now comes the fun part: you take the function signature, cut-and-paste it - into the macro, and add two commas - one between the return type and the - name, another between the name and the argument list. -* If you're mocking a const method, add a 4th parameter containing `(const)` - (the parentheses are required). -* Since you're overriding a virtual method, we suggest adding the `override` - keyword. For const methods the 4th parameter becomes `(const, override)`, - for non-const methods just `(override)`. This isn't mandatory. -* Repeat until all virtual functions you want to mock are done. (It goes - without saying that *all* pure virtual methods in your abstract class must - be either mocked or overridden.) - -After the process, you should have something like: - -```cpp -#include "gmock/gmock.h" // Brings in gMock. - -class MockTurtle : public Turtle { - public: - ... - MOCK_METHOD(void, PenUp, (), (override)); - MOCK_METHOD(void, PenDown, (), (override)); - MOCK_METHOD(void, Forward, (int distance), (override)); - MOCK_METHOD(void, Turn, (int degrees), (override)); - MOCK_METHOD(void, GoTo, (int x, int y), (override)); - MOCK_METHOD(int, GetX, (), (const, override)); - MOCK_METHOD(int, GetY, (), (const, override)); -}; -``` - -You don't need to define these mock methods somewhere else - the `MOCK_METHOD` -macro will generate the definitions for you. It's that simple! - -### Where to Put It - -When you define a mock class, you need to decide where to put its definition. -Some people put it in a `_test.cc`. This is fine when the interface being mocked -(say, `Foo`) is owned by the same person or team. Otherwise, when the owner of -`Foo` changes it, your test could break. (You can't really expect `Foo`'s -maintainer to fix every test that uses `Foo`, can you?) - -So, the rule of thumb is: if you need to mock `Foo` and it's owned by others, -define the mock class in `Foo`'s package (better, in a `testing` sub-package -such that you can clearly separate production code and testing utilities), put -it in a `.h` and a `cc_library`. Then everyone can reference them from their -tests. If `Foo` ever changes, there is only one copy of `MockFoo` to change, and -only tests that depend on the changed methods need to be fixed. - -Another way to do it: you can introduce a thin layer `FooAdaptor` on top of -`Foo` and code to this new interface. Since you own `FooAdaptor`, you can absorb -changes in `Foo` much more easily. While this is more work initially, carefully -choosing the adaptor interface can make your code easier to write and more -readable (a net win in the long run), as you can choose `FooAdaptor` to fit your -specific domain much better than `Foo` does. - -<!-- GOOGLETEST_CM0029 DO NOT DELETE --> - -## Using Mocks in Tests - -Once you have a mock class, using it is easy. The typical work flow is: - -1. Import the gMock names from the `testing` namespace such that you can use - them unqualified (You only have to do it once per file). Remember that - namespaces are a good idea. -2. Create some mock objects. -3. Specify your expectations on them (How many times will a method be called? - With what arguments? What should it do? etc.). -4. Exercise some code that uses the mocks; optionally, check the result using - googletest assertions. If a mock method is called more than expected or with - wrong arguments, you'll get an error immediately. -5. When a mock is destructed, gMock will automatically check whether all - expectations on it have been satisfied. - -Here's an example: - -```cpp -#include "path/to/mock-turtle.h" -#include "gmock/gmock.h" -#include "gtest/gtest.h" - -using ::testing::AtLeast; // #1 - -TEST(PainterTest, CanDrawSomething) { - MockTurtle turtle; // #2 - EXPECT_CALL(turtle, PenDown()) // #3 - .Times(AtLeast(1)); - - Painter painter(&turtle); // #4 - - EXPECT_TRUE(painter.DrawCircle(0, 0, 10)); // #5 -} -``` - -As you might have guessed, this test checks that `PenDown()` is called at least -once. If the `painter` object didn't call this method, your test will fail with -a message like this: - -```text -path/to/my_test.cc:119: Failure -Actual function call count doesn't match this expectation: -Actually: never called; -Expected: called at least once. -Stack trace: -... -``` - -**Tip 1:** If you run the test from an Emacs buffer, you can hit `<Enter>` on -the line number to jump right to the failed expectation. - -**Tip 2:** If your mock objects are never deleted, the final verification won't -happen. Therefore it's a good idea to turn on the heap checker in your tests -when you allocate mocks on the heap. You get that automatically if you use the -`gtest_main` library already. - -**Important note:** gMock requires expectations to be set **before** the mock -functions are called, otherwise the behavior is **undefined**. In particular, -you mustn't interleave `EXPECT_CALL()s` and calls to the mock functions. - -This means `EXPECT_CALL()` should be read as expecting that a call will occur -*in the future*, not that a call has occurred. Why does gMock work like that? -Well, specifying the expectation beforehand allows gMock to report a violation -as soon as it rises, when the context (stack trace, etc) is still available. -This makes debugging much easier. - -Admittedly, this test is contrived and doesn't do much. You can easily achieve -the same effect without using gMock. However, as we shall reveal soon, gMock -allows you to do *so much more* with the mocks. - -## Setting Expectations - -The key to using a mock object successfully is to set the *right expectations* -on it. If you set the expectations too strict, your test will fail as the result -of unrelated changes. If you set them too loose, bugs can slip through. You want -to do it just right such that your test can catch exactly the kind of bugs you -intend it to catch. gMock provides the necessary means for you to do it "just -right." - -### General Syntax - -In gMock we use the `EXPECT_CALL()` macro to set an expectation on a mock -method. The general syntax is: - -```cpp -EXPECT_CALL(mock_object, method(matchers)) - .Times(cardinality) - .WillOnce(action) - .WillRepeatedly(action); -``` - -The macro has two arguments: first the mock object, and then the method and its -arguments. Note that the two are separated by a comma (`,`), not a period (`.`). -(Why using a comma? The answer is that it was necessary for technical reasons.) -If the method is not overloaded, the macro can also be called without matchers: - -```cpp -EXPECT_CALL(mock_object, non-overloaded-method) - .Times(cardinality) - .WillOnce(action) - .WillRepeatedly(action); -``` - -This syntax allows the test writer to specify "called with any arguments" -without explicitly specifying the number or types of arguments. To avoid -unintended ambiguity, this syntax may only be used for methods which are not -overloaded - -Either form of the macro can be followed by some optional *clauses* that provide -more information about the expectation. We'll discuss how each clause works in -the coming sections. - -This syntax is designed to make an expectation read like English. For example, -you can probably guess that - -```cpp -using ::testing::Return; -... -EXPECT_CALL(turtle, GetX()) - .Times(5) - .WillOnce(Return(100)) - .WillOnce(Return(150)) - .WillRepeatedly(Return(200)); -``` - -says that the `turtle` object's `GetX()` method will be called five times, it -will return 100 the first time, 150 the second time, and then 200 every time. -Some people like to call this style of syntax a Domain-Specific Language (DSL). - -**Note:** Why do we use a macro to do this? Well it serves two purposes: first -it makes expectations easily identifiable (either by `gsearch` or by a human -reader), and second it allows gMock to include the source file location of a -failed expectation in messages, making debugging easier. - -### Matchers: What Arguments Do We Expect? - -When a mock function takes arguments, we may specify what arguments we are -expecting, for example: - -```cpp -// Expects the turtle to move forward by 100 units. -EXPECT_CALL(turtle, Forward(100)); -``` - -Oftentimes you do not want to be too specific. Remember that talk about tests -being too rigid? Over specification leads to brittle tests and obscures the -intent of tests. Therefore we encourage you to specify only what's necessary—no -more, no less. If you aren't interested in the value of an argument, write `_` -as the argument, which means "anything goes": - -```cpp -using ::testing::_; -... -// Expects that the turtle jumps to somewhere on the x=50 line. -EXPECT_CALL(turtle, GoTo(50, _)); -``` - -`_` is an instance of what we call **matchers**. A matcher is like a predicate -and can test whether an argument is what we'd expect. You can use a matcher -inside `EXPECT_CALL()` wherever a function argument is expected. `_` is a -convenient way of saying "any value". - -In the above examples, `100` and `50` are also matchers; implicitly, they are -the same as `Eq(100)` and `Eq(50)`, which specify that the argument must be -equal (using `operator==`) to the matcher argument. There are many -[built-in matchers](cheat_sheet.md#MatcherList) for common types (as well as -[custom matchers](cook_book.md#NewMatchers)); for example: - -```cpp -using ::testing::Ge; -... -// Expects the turtle moves forward by at least 100. -EXPECT_CALL(turtle, Forward(Ge(100))); -``` - -If you don't care about *any* arguments, rather than specify `_` for each of -them you may instead omit the parameter list: - -```cpp -// Expects the turtle to move forward. -EXPECT_CALL(turtle, Forward); -// Expects the turtle to jump somewhere. -EXPECT_CALL(turtle, GoTo); -``` - -This works for all non-overloaded methods; if a method is overloaded, you need -to help gMock resolve which overload is expected by specifying the number of -arguments and possibly also the -[types of the arguments](cook_book.md#SelectOverload). - -### Cardinalities: How Many Times Will It Be Called? - -The first clause we can specify following an `EXPECT_CALL()` is `Times()`. We -call its argument a **cardinality** as it tells *how many times* the call should -occur. It allows us to repeat an expectation many times without actually writing -it as many times. More importantly, a cardinality can be "fuzzy", just like a -matcher can be. This allows a user to express the intent of a test exactly. - -An interesting special case is when we say `Times(0)`. You may have guessed - it -means that the function shouldn't be called with the given arguments at all, and -gMock will report a googletest failure whenever the function is (wrongfully) -called. - -We've seen `AtLeast(n)` as an example of fuzzy cardinalities earlier. For the -list of built-in cardinalities you can use, see -[here](cheat_sheet.md#CardinalityList). - -The `Times()` clause can be omitted. **If you omit `Times()`, gMock will infer -the cardinality for you.** The rules are easy to remember: - -* If **neither** `WillOnce()` **nor** `WillRepeatedly()` is in the - `EXPECT_CALL()`, the inferred cardinality is `Times(1)`. -* If there are *n* `WillOnce()`'s but **no** `WillRepeatedly()`, where *n* >= - 1, the cardinality is `Times(n)`. -* If there are *n* `WillOnce()`'s and **one** `WillRepeatedly()`, where *n* >= - 0, the cardinality is `Times(AtLeast(n))`. - -**Quick quiz:** what do you think will happen if a function is expected to be -called twice but actually called four times? - -### Actions: What Should It Do? - -Remember that a mock object doesn't really have a working implementation? We as -users have to tell it what to do when a method is invoked. This is easy in -gMock. - -First, if the return type of a mock function is a built-in type or a pointer, -the function has a **default action** (a `void` function will just return, a -`bool` function will return `false`, and other functions will return 0). In -addition, in C++ 11 and above, a mock function whose return type is -default-constructible (i.e. has a default constructor) has a default action of -returning a default-constructed value. If you don't say anything, this behavior -will be used. - -Second, if a mock function doesn't have a default action, or the default action -doesn't suit you, you can specify the action to be taken each time the -expectation matches using a series of `WillOnce()` clauses followed by an -optional `WillRepeatedly()`. For example, - -```cpp -using ::testing::Return; -... -EXPECT_CALL(turtle, GetX()) - .WillOnce(Return(100)) - .WillOnce(Return(200)) - .WillOnce(Return(300)); -``` - -says that `turtle.GetX()` will be called *exactly three times* (gMock inferred -this from how many `WillOnce()` clauses we've written, since we didn't -explicitly write `Times()`), and will return 100, 200, and 300 respectively. - -```cpp -using ::testing::Return; -... -EXPECT_CALL(turtle, GetY()) - .WillOnce(Return(100)) - .WillOnce(Return(200)) - .WillRepeatedly(Return(300)); -``` - -says that `turtle.GetY()` will be called *at least twice* (gMock knows this as -we've written two `WillOnce()` clauses and a `WillRepeatedly()` while having no -explicit `Times()`), will return 100 and 200 respectively the first two times, -and 300 from the third time on. - -Of course, if you explicitly write a `Times()`, gMock will not try to infer the -cardinality itself. What if the number you specified is larger than there are -`WillOnce()` clauses? Well, after all `WillOnce()`s are used up, gMock will do -the *default* action for the function every time (unless, of course, you have a -`WillRepeatedly()`.). - -What can we do inside `WillOnce()` besides `Return()`? You can return a -reference using `ReturnRef(*variable*)`, or invoke a pre-defined function, among -[others](cook_book.md#using-actions). - -**Important note:** The `EXPECT_CALL()` statement evaluates the action clause -only once, even though the action may be performed many times. Therefore you -must be careful about side effects. The following may not do what you want: - -```cpp -using ::testing::Return; -... -int n = 100; -EXPECT_CALL(turtle, GetX()) - .Times(4) - .WillRepeatedly(Return(n++)); -``` - -Instead of returning 100, 101, 102, ..., consecutively, this mock function will -always return 100 as `n++` is only evaluated once. Similarly, `Return(new Foo)` -will create a new `Foo` object when the `EXPECT_CALL()` is executed, and will -return the same pointer every time. If you want the side effect to happen every -time, you need to define a custom action, which we'll teach in the -[cook book](http://<!-- GOOGLETEST_CM0012 DO NOT DELETE -->). - -Time for another quiz! What do you think the following means? - -```cpp -using ::testing::Return; -... -EXPECT_CALL(turtle, GetY()) - .Times(4) - .WillOnce(Return(100)); -``` - -Obviously `turtle.GetY()` is expected to be called four times. But if you think -it will return 100 every time, think twice! Remember that one `WillOnce()` -clause will be consumed each time the function is invoked and the default action -will be taken afterwards. So the right answer is that `turtle.GetY()` will -return 100 the first time, but **return 0 from the second time on**, as -returning 0 is the default action for `int` functions. - -### Using Multiple Expectations {#MultiExpectations} - -So far we've only shown examples where you have a single expectation. More -realistically, you'll specify expectations on multiple mock methods which may be -from multiple mock objects. - -By default, when a mock method is invoked, gMock will search the expectations in -the **reverse order** they are defined, and stop when an active expectation that -matches the arguments is found (you can think of it as "newer rules override -older ones."). If the matching expectation cannot take any more calls, you will -get an upper-bound-violated failure. Here's an example: - -```cpp -using ::testing::_; -... -EXPECT_CALL(turtle, Forward(_)); // #1 -EXPECT_CALL(turtle, Forward(10)) // #2 - .Times(2); -``` - -If `Forward(10)` is called three times in a row, the third time it will be an -error, as the last matching expectation (#2) has been saturated. If, however, -the third `Forward(10)` call is replaced by `Forward(20)`, then it would be OK, -as now #1 will be the matching expectation. - -**Note:** Why does gMock search for a match in the *reverse* order of the -expectations? The reason is that this allows a user to set up the default -expectations in a mock object's constructor or the test fixture's set-up phase -and then customize the mock by writing more specific expectations in the test -body. So, if you have two expectations on the same method, you want to put the -one with more specific matchers **after** the other, or the more specific rule -would be shadowed by the more general one that comes after it. - -**Tip:** It is very common to start with a catch-all expectation for a method -and `Times(AnyNumber())` (omitting arguments, or with `_` for all arguments, if -overloaded). This makes any calls to the method expected. This is not necessary -for methods that are not mentioned at all (these are "uninteresting"), but is -useful for methods that have some expectations, but for which other calls are -ok. See -[Understanding Uninteresting vs Unexpected Calls](cook_book.md#uninteresting-vs-unexpected). - -### Ordered vs Unordered Calls {#OrderedCalls} - -By default, an expectation can match a call even though an earlier expectation -hasn't been satisfied. In other words, the calls don't have to occur in the -order the expectations are specified. - -Sometimes, you may want all the expected calls to occur in a strict order. To -say this in gMock is easy: - -```cpp -using ::testing::InSequence; -... -TEST(FooTest, DrawsLineSegment) { - ... - { - InSequence seq; - - EXPECT_CALL(turtle, PenDown()); - EXPECT_CALL(turtle, Forward(100)); - EXPECT_CALL(turtle, PenUp()); - } - Foo(); -} -``` - -By creating an object of type `InSequence`, all expectations in its scope are -put into a *sequence* and have to occur *sequentially*. Since we are just -relying on the constructor and destructor of this object to do the actual work, -its name is really irrelevant. - -In this example, we test that `Foo()` calls the three expected functions in the -order as written. If a call is made out-of-order, it will be an error. - -(What if you care about the relative order of some of the calls, but not all of -them? Can you specify an arbitrary partial order? The answer is ... yes! The -details can be found [here](cook_book.md#OrderedCalls).) - -### All Expectations Are Sticky (Unless Said Otherwise) {#StickyExpectations} - -Now let's do a quick quiz to see how well you can use this mock stuff already. -How would you test that the turtle is asked to go to the origin *exactly twice* -(you want to ignore any other instructions it receives)? - -After you've come up with your answer, take a look at ours and compare notes -(solve it yourself first - don't cheat!): - -```cpp -using ::testing::_; -using ::testing::AnyNumber; -... -EXPECT_CALL(turtle, GoTo(_, _)) // #1 - .Times(AnyNumber()); -EXPECT_CALL(turtle, GoTo(0, 0)) // #2 - .Times(2); -``` - -Suppose `turtle.GoTo(0, 0)` is called three times. In the third time, gMock will -see that the arguments match expectation #2 (remember that we always pick the -last matching expectation). Now, since we said that there should be only two -such calls, gMock will report an error immediately. This is basically what we've -told you in the [Using Multiple Expectations](#MultiExpectations) section above. - -This example shows that **expectations in gMock are "sticky" by default**, in -the sense that they remain active even after we have reached their invocation -upper bounds. This is an important rule to remember, as it affects the meaning -of the spec, and is **different** to how it's done in many other mocking -frameworks (Why'd we do that? Because we think our rule makes the common cases -easier to express and understand.). - -Simple? Let's see if you've really understood it: what does the following code -say? - -```cpp -using ::testing::Return; -... -for (int i = n; i > 0; i--) { - EXPECT_CALL(turtle, GetX()) - .WillOnce(Return(10*i)); -} -``` - -If you think it says that `turtle.GetX()` will be called `n` times and will -return 10, 20, 30, ..., consecutively, think twice! The problem is that, as we -said, expectations are sticky. So, the second time `turtle.GetX()` is called, -the last (latest) `EXPECT_CALL()` statement will match, and will immediately -lead to an "upper bound violated" error - this piece of code is not very useful! - -One correct way of saying that `turtle.GetX()` will return 10, 20, 30, ..., is -to explicitly say that the expectations are *not* sticky. In other words, they -should *retire* as soon as they are saturated: - -```cpp -using ::testing::Return; -... -for (int i = n; i > 0; i--) { - EXPECT_CALL(turtle, GetX()) - .WillOnce(Return(10*i)) - .RetiresOnSaturation(); -} -``` - -And, there's a better way to do it: in this case, we expect the calls to occur -in a specific order, and we line up the actions to match the order. Since the -order is important here, we should make it explicit using a sequence: - -```cpp -using ::testing::InSequence; -using ::testing::Return; -... -{ - InSequence s; - - for (int i = 1; i <= n; i++) { - EXPECT_CALL(turtle, GetX()) - .WillOnce(Return(10*i)) - .RetiresOnSaturation(); - } -} -``` - -By the way, the other situation where an expectation may *not* be sticky is when -it's in a sequence - as soon as another expectation that comes after it in the -sequence has been used, it automatically retires (and will never be used to -match any call). - -### Uninteresting Calls - -A mock object may have many methods, and not all of them are that interesting. -For example, in some tests we may not care about how many times `GetX()` and -`GetY()` get called. - -In gMock, if you are not interested in a method, just don't say anything about -it. If a call to this method occurs, you'll see a warning in the test output, -but it won't be a failure. This is called "naggy" behavior; to change, see -[The Nice, the Strict, and the Naggy](cook_book.md#NiceStrictNaggy). diff --git a/googlemock/docs/gmock_faq.md b/googlemock/docs/gmock_faq.md deleted file mode 100644 index 14acae5..0000000 --- a/googlemock/docs/gmock_faq.md +++ /dev/null @@ -1,398 +0,0 @@ -## Legacy gMock FAQ {#GMockFaq} - -<!-- GOOGLETEST_CM0021 DO NOT DELETE --> - -<!-- GOOGLETEST_CM0035 DO NOT DELETE --> - -### When I call a method on my mock object, the method for the real object is invoked instead. What's the problem? - -In order for a method to be mocked, it must be *virtual*, unless you use the -[high-perf dependency injection technique](cook_book.md#MockingNonVirtualMethods). - -### Can I mock a variadic function? - -You cannot mock a variadic function (i.e. a function taking ellipsis (`...`) -arguments) directly in gMock. - -The problem is that in general, there is *no way* for a mock object to know how -many arguments are passed to the variadic method, and what the arguments' types -are. Only the *author of the base class* knows the protocol, and we cannot look -into his or her head. - -Therefore, to mock such a function, the *user* must teach the mock object how to -figure out the number of arguments and their types. One way to do it is to -provide overloaded versions of the function. - -Ellipsis arguments are inherited from C and not really a C++ feature. They are -unsafe to use and don't work with arguments that have constructors or -destructors. Therefore we recommend to avoid them in C++ as much as possible. - -### MSVC gives me warning C4301 or C4373 when I define a mock method with a const parameter. Why? - -If you compile this using Microsoft Visual C++ 2005 SP1: - -```cpp -class Foo { - ... - virtual void Bar(const int i) = 0; -}; - -class MockFoo : public Foo { - ... - MOCK_METHOD(void, Bar, (const int i), (override)); -}; -``` - -You may get the following warning: - -```shell -warning C4301: 'MockFoo::Bar': overriding virtual function only differs from 'Foo::Bar' by const/volatile qualifier -``` - -This is a MSVC bug. The same code compiles fine with gcc, for example. If you -use Visual C++ 2008 SP1, you would get the warning: - -```shell -warning C4373: 'MockFoo::Bar': virtual function overrides 'Foo::Bar', previous versions of the compiler did not override when parameters only differed by const/volatile qualifiers -``` - -In C++, if you *declare* a function with a `const` parameter, the `const` -modifier is ignored. Therefore, the `Foo` base class above is equivalent to: - -```cpp -class Foo { - ... - virtual void Bar(int i) = 0; // int or const int? Makes no difference. -}; -``` - -In fact, you can *declare* `Bar()` with an `int` parameter, and define it with a -`const int` parameter. The compiler will still match them up. - -Since making a parameter `const` is meaningless in the method declaration, we -recommend to remove it in both `Foo` and `MockFoo`. That should workaround the -VC bug. - -Note that we are talking about the *top-level* `const` modifier here. If the -function parameter is passed by pointer or reference, declaring the pointee or -referee as `const` is still meaningful. For example, the following two -declarations are *not* equivalent: - -```cpp -void Bar(int* p); // Neither p nor *p is const. -void Bar(const int* p); // p is not const, but *p is. -``` - -<!-- GOOGLETEST_CM0030 DO NOT DELETE --> - -### I can't figure out why gMock thinks my expectations are not satisfied. What should I do? - -You might want to run your test with `--gmock_verbose=info`. This flag lets -gMock print a trace of every mock function call it receives. By studying the -trace, you'll gain insights on why the expectations you set are not met. - -If you see the message "The mock function has no default action set, and its -return type has no default value set.", then try -[adding a default action](for_dummies.md#DefaultValue). Due to a known issue, -unexpected calls on mocks without default actions don't print out a detailed -comparison between the actual arguments and the expected arguments. - -### My program crashed and `ScopedMockLog` spit out tons of messages. Is it a gMock bug? - -gMock and `ScopedMockLog` are likely doing the right thing here. - -When a test crashes, the failure signal handler will try to log a lot of -information (the stack trace, and the address map, for example). The messages -are compounded if you have many threads with depth stacks. When `ScopedMockLog` -intercepts these messages and finds that they don't match any expectations, it -prints an error for each of them. - -You can learn to ignore the errors, or you can rewrite your expectations to make -your test more robust, for example, by adding something like: - -```cpp -using ::testing::AnyNumber; -using ::testing::Not; -... - // Ignores any log not done by us. - EXPECT_CALL(log, Log(_, Not(EndsWith("/my_file.cc")), _)) - .Times(AnyNumber()); -``` - -### How can I assert that a function is NEVER called? - -```cpp -using ::testing::_; -... - EXPECT_CALL(foo, Bar(_)) - .Times(0); -``` - -<!-- GOOGLETEST_CM0031 DO NOT DELETE --> - -### I have a failed test where gMock tells me TWICE that a particular expectation is not satisfied. Isn't this redundant? - -When gMock detects a failure, it prints relevant information (the mock function -arguments, the state of relevant expectations, and etc) to help the user debug. -If another failure is detected, gMock will do the same, including printing the -state of relevant expectations. - -Sometimes an expectation's state didn't change between two failures, and you'll -see the same description of the state twice. They are however *not* redundant, -as they refer to *different points in time*. The fact they are the same *is* -interesting information. - -### I get a heapcheck failure when using a mock object, but using a real object is fine. What can be wrong? - -Does the class (hopefully a pure interface) you are mocking have a virtual -destructor? - -Whenever you derive from a base class, make sure its destructor is virtual. -Otherwise Bad Things will happen. Consider the following code: - -```cpp -class Base { - public: - // Not virtual, but should be. - ~Base() { ... } - ... -}; - -class Derived : public Base { - public: - ... - private: - std::string value_; -}; - -... - Base* p = new Derived; - ... - delete p; // Surprise! ~Base() will be called, but ~Derived() will not - // - value_ is leaked. -``` - -By changing `~Base()` to virtual, `~Derived()` will be correctly called when -`delete p` is executed, and the heap checker will be happy. - -### The "newer expectations override older ones" rule makes writing expectations awkward. Why does gMock do that? - -When people complain about this, often they are referring to code like: - -```cpp -using ::testing::Return; -... - // foo.Bar() should be called twice, return 1 the first time, and return - // 2 the second time. However, I have to write the expectations in the - // reverse order. This sucks big time!!! - EXPECT_CALL(foo, Bar()) - .WillOnce(Return(2)) - .RetiresOnSaturation(); - EXPECT_CALL(foo, Bar()) - .WillOnce(Return(1)) - .RetiresOnSaturation(); -``` - -The problem, is that they didn't pick the **best** way to express the test's -intent. - -By default, expectations don't have to be matched in *any* particular order. If -you want them to match in a certain order, you need to be explicit. This is -gMock's (and jMock's) fundamental philosophy: it's easy to accidentally -over-specify your tests, and we want to make it harder to do so. - -There are two better ways to write the test spec. You could either put the -expectations in sequence: - -```cpp -using ::testing::Return; -... - // foo.Bar() should be called twice, return 1 the first time, and return - // 2 the second time. Using a sequence, we can write the expectations - // in their natural order. - { - InSequence s; - EXPECT_CALL(foo, Bar()) - .WillOnce(Return(1)) - .RetiresOnSaturation(); - EXPECT_CALL(foo, Bar()) - .WillOnce(Return(2)) - .RetiresOnSaturation(); - } -``` - -or you can put the sequence of actions in the same expectation: - -```cpp -using ::testing::Return; -... - // foo.Bar() should be called twice, return 1 the first time, and return - // 2 the second time. - EXPECT_CALL(foo, Bar()) - .WillOnce(Return(1)) - .WillOnce(Return(2)) - .RetiresOnSaturation(); -``` - -Back to the original questions: why does gMock search the expectations (and -`ON_CALL`s) from back to front? Because this allows a user to set up a mock's -behavior for the common case early (e.g. in the mock's constructor or the test -fixture's set-up phase) and customize it with more specific rules later. If -gMock searches from front to back, this very useful pattern won't be possible. - -### gMock prints a warning when a function without EXPECT_CALL is called, even if I have set its behavior using ON_CALL. Would it be reasonable not to show the warning in this case? - -When choosing between being neat and being safe, we lean toward the latter. So -the answer is that we think it's better to show the warning. - -Often people write `ON_CALL`s in the mock object's constructor or `SetUp()`, as -the default behavior rarely changes from test to test. Then in the test body -they set the expectations, which are often different for each test. Having an -`ON_CALL` in the set-up part of a test doesn't mean that the calls are expected. -If there's no `EXPECT_CALL` and the method is called, it's possibly an error. If -we quietly let the call go through without notifying the user, bugs may creep in -unnoticed. - -If, however, you are sure that the calls are OK, you can write - -```cpp -using ::testing::_; -... - EXPECT_CALL(foo, Bar(_)) - .WillRepeatedly(...); -``` - -instead of - -```cpp -using ::testing::_; -... - ON_CALL(foo, Bar(_)) - .WillByDefault(...); -``` - -This tells gMock that you do expect the calls and no warning should be printed. - -Also, you can control the verbosity by specifying `--gmock_verbose=error`. Other -values are `info` and `warning`. If you find the output too noisy when -debugging, just choose a less verbose level. - -### How can I delete the mock function's argument in an action? - -If your mock function takes a pointer argument and you want to delete that -argument, you can use testing::DeleteArg<N>() to delete the N'th (zero-indexed) -argument: - -```cpp -using ::testing::_; - ... - MOCK_METHOD(void, Bar, (X* x, const Y& y)); - ... - EXPECT_CALL(mock_foo_, Bar(_, _)) - .WillOnce(testing::DeleteArg<0>())); -``` - -### How can I perform an arbitrary action on a mock function's argument? - -If you find yourself needing to perform some action that's not supported by -gMock directly, remember that you can define your own actions using -[`MakeAction()`](#NewMonoActions) or -[`MakePolymorphicAction()`](#NewPolyActions), or you can write a stub function -and invoke it using [`Invoke()`](#FunctionsAsActions). - -```cpp -using ::testing::_; -using ::testing::Invoke; - ... - MOCK_METHOD(void, Bar, (X* p)); - ... - EXPECT_CALL(mock_foo_, Bar(_)) - .WillOnce(Invoke(MyAction(...))); -``` - -### My code calls a static/global function. Can I mock it? - -You can, but you need to make some changes. - -In general, if you find yourself needing to mock a static function, it's a sign -that your modules are too tightly coupled (and less flexible, less reusable, -less testable, etc). You are probably better off defining a small interface and -call the function through that interface, which then can be easily mocked. It's -a bit of work initially, but usually pays for itself quickly. - -This Google Testing Blog -[post](https://testing.googleblog.com/2008/06/defeat-static-cling.html) says it -excellently. Check it out. - -### My mock object needs to do complex stuff. It's a lot of pain to specify the actions. gMock sucks! - -I know it's not a question, but you get an answer for free any way. :-) - -With gMock, you can create mocks in C++ easily. And people might be tempted to -use them everywhere. Sometimes they work great, and sometimes you may find them, -well, a pain to use. So, what's wrong in the latter case? - -When you write a test without using mocks, you exercise the code and assert that -it returns the correct value or that the system is in an expected state. This is -sometimes called "state-based testing". - -Mocks are great for what some call "interaction-based" testing: instead of -checking the system state at the very end, mock objects verify that they are -invoked the right way and report an error as soon as it arises, giving you a -handle on the precise context in which the error was triggered. This is often -more effective and economical to do than state-based testing. - -If you are doing state-based testing and using a test double just to simulate -the real object, you are probably better off using a fake. Using a mock in this -case causes pain, as it's not a strong point for mocks to perform complex -actions. If you experience this and think that mocks suck, you are just not -using the right tool for your problem. Or, you might be trying to solve the -wrong problem. :-) - -### I got a warning "Uninteresting function call encountered - default action taken.." Should I panic? - -By all means, NO! It's just an FYI. :-) - -What it means is that you have a mock function, you haven't set any expectations -on it (by gMock's rule this means that you are not interested in calls to this -function and therefore it can be called any number of times), and it is called. -That's OK - you didn't say it's not OK to call the function! - -What if you actually meant to disallow this function to be called, but forgot to -write `EXPECT_CALL(foo, Bar()).Times(0)`? While one can argue that it's the -user's fault, gMock tries to be nice and prints you a note. - -So, when you see the message and believe that there shouldn't be any -uninteresting calls, you should investigate what's going on. To make your life -easier, gMock dumps the stack trace when an uninteresting call is encountered. -From that you can figure out which mock function it is, and how it is called. - -### I want to define a custom action. Should I use Invoke() or implement the ActionInterface interface? - -Either way is fine - you want to choose the one that's more convenient for your -circumstance. - -Usually, if your action is for a particular function type, defining it using -`Invoke()` should be easier; if your action can be used in functions of -different types (e.g. if you are defining `Return(*value*)`), -`MakePolymorphicAction()` is easiest. Sometimes you want precise control on what -types of functions the action can be used in, and implementing `ActionInterface` -is the way to go here. See the implementation of `Return()` in -`testing/base/public/gmock-actions.h` for an example. - -### I use SetArgPointee() in WillOnce(), but gcc complains about "conflicting return type specified". What does it mean? - -You got this error as gMock has no idea what value it should return when the -mock method is called. `SetArgPointee()` says what the side effect is, but -doesn't say what the return value should be. You need `DoAll()` to chain a -`SetArgPointee()` with a `Return()` that provides a value appropriate to the API -being mocked. - -See this [recipe](cook_book.md#mocking-side-effects) for more details and an -example. - -### I have a huge mock class, and Microsoft Visual C++ runs out of memory when compiling it. What can I do? - -We've noticed that when the `/clr` compiler flag is used, Visual C++ uses 5~6 -times as much memory when compiling a mock class. We suggest to avoid `/clr` -when compiling native C++ mocks. diff --git a/googlemock/docs/guide.md b/googlemock/docs/guide.md deleted file mode 100644 index 3e74594..0000000 --- a/googlemock/docs/guide.md +++ /dev/null @@ -1,49 +0,0 @@ -# googletest gMock Users Guide - -go/gmockguide - -Welcome to googletest: Google's C++ testing and mocking framework. gMock is a -mocking part of googletest. - -* [OSS Version](https://github.com/google/googletest) -* [Google3](http://google3/third_party/googletest/) - -* If you are new to gMock, start with [*gMock for Dummies*](for_dummies.md) to - learn the basic usage. - -* Read [gMock Cookbook](cook_book.md) to learn more advanced usage and useful - tips. - -* For a quick reference, check out [gMock Cheat Sheet](cheat_sheet.md). - -* If you have questions, search [gMock FAQ](#GMockFaq) and the gmock-users@ - archive before sending them to gmock-users@. - -<!-- GOOGLETEST_CM0035 DO NOT DELETE --> - -<!--#include file="for_dummies.md"--> - -#### Side Effects - -<!-- mdformat off(github rendering does not support multiline tables) --> -| Matcher | Description | -| :--------------------------------- | :-------------------------------------- | -| `Assign(&variable, value)` | Assign `value` to variable. | -| `DeleteArg<N>()` | Delete the `N`-th (0-based) argument, which must be a pointer. | -| `SaveArg<N>(pointer)` | Save the `N`-th (0-based) argument to `*pointer`. | -| `SaveArgPointee<N>(pointer)` | Save the value pointed to by the `N`-th (0-based) argument to `*pointer`. | -| `SetArgReferee<N>(value)` | Assign `value` to the variable referenced by the `N`-th (0-based) argument. | -| `SetArgPointee<N>(value)` | Assign `value` to the variable pointed by the `N`-th (0-based) argument. | -| `SetArgumentPointee<N>(value)` | Same as `SetArgPointee<N>(value)`. Deprecated. Will be removed in v1.7.0. | -| `SetArrayArgument<N>(first, last)` | Copies the elements in source range [`first`, `last`) to the array pointed to by the `N`-th (0-based) argument, which can be either a pointer or an iterator. The action does not take ownership of the elements in the source range. | -| `SetErrnoAndReturn(error, value)` | Set `errno` to `error` and return `value`. | -| `Throw(exception)` | Throws the given exception, which can be any copyable value. Available since v1.1.0. | -<!-- mdformat on --> - -* When compiling with exceptions in google3, it's not enough to specify - `-fexceptions` to copts in your cc_test target. That flag will not be - inherited by gmock, and various headers will be compiled both with and - without `-fexceptions` causing subtle bugs. Instead you must pass - `--copt=-fexceptions` to the blaze command so the flag gets passed to all - targets... but this is Google and we don't use exceptions so it shouldn't - really be an issue. diff --git a/googlemock/docs/index.md b/googlemock/docs/index.md deleted file mode 100644 index cc73e83..0000000 --- a/googlemock/docs/index.md +++ /dev/null @@ -1,127 +0,0 @@ -# googletest Home - -go/gmock - -Googletest is Google's C++ testing and mocking framework. Please note that there -are legacy names you may encounter "gUnit" and "gMock" - these names are now -merged into "googletest" - -<!-- GOOGLETEST_CM0035 DO NOT DELETE --> - -## Testimonials - -> "I'm really enjoying trying it, and it's amazing to me how far you've taken -> this in C++. It's changed the way I program (and therefore changed my life ;), -> and one of my teams has adopted it for all/most tests (and I'm working on the -> other)." \ -> -- *Derek Thomson*, Google Mountain View - -<section></section> - -> "I started using mocks with EasyMock in Java a few years ago and found them -> **invaluable** for making unit testing as painless and effective as possible. -> I'm very glad (and amazed) to see you've managed to create something similar -> for C++. It's making the transition much more pleasant." \ -> -- *David Harkness*, Google Mountain View - -<section></section> - -> "I #included `gmock.h` and lived to tell the tale... Kept me from having to -> depend on `MockBigtable` thus far, which is **huge**." \ -> -- *Matthew Simmons*, Google NYC - -<section></section> - -> "I like the approach of `EXPECT_CALL` much more than EasyMock's mock modes -> (record, replay). It's the best way to ensure the user will never forget to -> verify the expectations: do it automatically!" \ -> -- *Tiago Silverira*, Google Brazil - -<section></section> - -> "It's by far the best mocking library for C++, by a long-shot." \ -> -- *Joe Walnes*, co-creator of jMock, Google London - -## Learning googletest mocking - -Please see the [*googletest Users Guide*](guide.md) for the combined gMock -mocking documentation. - -## Resources for Users - -* More docs: - * [Interview with gMock's Creator](http://www.corp.google.com/eng/testing/codegreen/v10/gMock.htm) - on the - [Feb 2008](http://www.corp.google.com/eng/testing/codegreen/v10/index.htm) - issue of [Code Green](http://go/codegreen) - discusses gMock's history - and philosophy. - * "Mockers of the (C++) world, delight!": TotT - [episode 66](http://big.corp.google.com/~jmcmaster/testing/2007/12/episode-68-mockers-of-c-world-delight.html) - - quick intro on gMock's benefits and usage - * "Mock logs better than gold": TotT - [episode 76](http://big.corp.google.com/~jmcmaster/testing/2008/02/episode-76-mock-logs-better-than-gold_21.html) - - how to test LOGs using gMock - * "Testing legacy code gently": TotT - [episode 84](http://big.corp.google.com/~jmcmaster/testing/2008/04/episode-84-testing-legacy-code-gently.html) - - using mock callbacks to test legacy code without a big refactoring - * "Literate testing with matchers": TotT - [episode 135](http://big.corp.google.com/~jmcmaster/testing/2009/06/episode-135-literate-testing-with_08.html) - - using matchers to get readable test code and readable test messages - * "Making a perfect matcher": TotT - [episode 139](http://big.corp.google.com/~jmcmaster/testing/2009/07/episode-139-making-perfect-matcher.html) - - defining custom matchers easily -* Talks - * "Declarative C++ Testing Using DSLs" talk (6/4/2008): - [abstract](https://wiki.corp.google.com/twiki/bin/view/Main/WanTalks#Declarative_C_Testing_Using_DSLs), - [slides](http://wiki.corp.google.com/twiki/pub/Main/WanTalks/0806-declarative-cpp-testing.xul#Eva) - (requires Firefox) - gMock's design and implementation tricks - * "Mocks made easy in C++ and Java" talk (4/23/2008): - [slides](http://go/MockTalk), - [fish](http://fish.corp.google.com/talks/8729/) - * "C++ mocks made easy - an introduction to gMock" talk (1/22/2008)): - [slides](http://wiki.corp.google.com/twiki/pub/Main/WanTalks/0801-mv-gmock.xul#eva) - (requires Firefox), - [video](https://video.google.com/a/google.com/?AuthEventSource=SSO#/Play/contentId=bd07003d4193a646) - * "A preview to gMock" talk (6/28/2007): - [PowerPoint slides](http://wiki.corp.google.com/twiki/pub/Main/WanTalks/0706-beijing-gmock-preview.ppt) -* Tools - * `/google/src/head/depot/google3/third_party/googletest/googlemock/scripts/generator/gmock_gen.py - *your.h ClassNames*` generates mocks for the given base classes (if no - class name is given, all classes in the file are emitted). -* Mocks - * [mock-log.h](http://s/?fileprint=//depot/google3/testing/base/public/mock-log.h) - - a sample on using gMock to create a mock class - * [gmock-sample-mock-log.cc](http://s/?fileprint=//depot/google3/testing/base/internal/gmock-sample-mock-log.cc) - - a sample on using gMock to test LOG()s -* Folks - * Meet the - [users](http://piano.kir.corp.google.com:8080/lica/?e=use%3Agmock). - * `gmock-users` list: - [subscribe](https://groups.google.com/a/google.com/group/gmock-users/topics), - [archive](https://groups.google.com/a/google.com/group/gmock-users/topics), - [smile!](http://piano.kir.corp.google.com:8080/lica/?e=gmock-users) Send - questions here if you still need help after consulting the on-line docs. - * `gmock-announce` list: - [subscribe](https://groups.google.com/a/google.com/group/gmock-announce/topics) - to this instead of `gmock-users` if you are interested in announcements - only. - -## Resources for Contributors - -* [Dashboard](http://unittest.corp.google.com/project/gunit-gmock/) -* [*gMock Design*](design.md) (go/gmockdesign) - the design doc -* `c-mock-dev` list (deprecated) - - [old archive](https://mailman.corp.google.com/pipermail/c/c-mock-dev/), - [new archive](https://g.corp.google.com/group/c-mock-dev-archive) -* `opensource-gmock` list - discussions on the development of gMock: - [subscribe](https://groups.google.com/a/google.com/group/opensource-gmock/subscribe), - [archive](https://g.corp.google.com/group/opensource-gmock-archive), - [smile!](http://piano.kir.corp.google.com:8080/lica/?e=opensource-gmock) - -## Acknowledgments - -We'd like to thank the following people for their contribution to gMock: Piotr -Kaminski, Jeffrey Yasskin (who/jyasskin), Joe Walnes, Bradford Cross, Keith Ray, -Craig Silverstein, Matthew Simmons (who/simmonmt), Hal Burch (who/hburch), Russ -Rufer, Rushabh Doshi (who/rdoshi), Gene Volovich (who/genev), Mike Bland, Neal -Norwitz (who/nnorwitz), Mark Zuber, Vadim Berman (who/vadimb). diff --git a/googlemock/docs/overview.md b/googlemock/docs/overview.md deleted file mode 100644 index 0c77dfa..0000000 --- a/googlemock/docs/overview.md +++ /dev/null @@ -1,111 +0,0 @@ -# GMock - -<!-- GOOGLETEST_CM0035 DO NOT DELETE --> - -## What is gMock? - -gMock is Google's framework for creating and using C++ mock classes. It helps -you design better systems and write better tests. A mock object is an object -that you use in a test instead of a real object. A mock object implements the -same interface as a real object but lets you specify at run time how the object -will be used. When you write tests that use a mock, you define expectations -about how the mock's methods will be called. Your test then verifies how your -real code behaves when interacting with the mock. See the -[Mock Objects Best Practices Guide](http://go/mock-objects#mocks-stubs-fakes) -for a comparison of mocks with stubs, fakes, and other kinds of test doubles. - -For example, gMock provides a simple syntax for declaring "I expect the -RetryQuery method on this mock object to be called three times in the course of -this test". Your test will fail if the expectation isn't met. - -The gMock library provides a mock framework for C++ similar to jMock or -EasyMock[?](http://go/easymock-codelab) for Java. In gMock you use macros to -define methods for your mock objects and set expectations for those methods. -gMock runs on Linux, Windows, and Mac OS X. - -## What is gMock good for? - -Mocks in general are good for: - -- prototyping and designing new code and APIs. -- removing unnecessary, expensive, or unreliable dependencies from your tests. - -gMock in particular is good for writing quality C++ mocks. Without the help of a -mocking framework like gMock, good C++ mocks are hard to create. - -## What is gMock NOT good for? - -gMock is not good for testing the behavior of dependencies. The point of testing -with mocks is to test the classes that use the mocks, not the mocks themselves. -Objects that have working toy implementations are called fakes instead of mocks. -For example, you could use an in-memory file system to fake disk operations. - -Mocks aren't useful for very simple classes like -[Dumb Data Objects](http://big.corp.google.com/~jmcmaster/testing/2011/04/episode-220-blast-from-tott-past-dont.html). -If it's more trouble to use a mock than the real class, just use the real class. - -## Who uses gMock? - -There are over 30K tests using gmock. Virtually every C++ test at Google that -needs a mock object uses gMock. - -## Practical matters - -gMock is bundled with [gUnit](/third_party/googletest/googletest/docs/). To use -gMock, -[include a dependency](/third_party/googletest/googletest/docs/howto_cpp#LinuxTarget) -on `//testing/base/public:gunit` in the BUILD rule for your mocks, and use the -following include statement in the file that defines your mock class: - -``` -#include "gmock/gmock.h" -``` - - | ---------------------------- | ------------------------------------------ -**Implementation language** | C++ -**Code location** | google3/third_party/googletest/googlemock/ -**Build target** | //testing/base/public:gunit - -## Best practices - -Use [dependency injection](http://en.wikipedia.org/wiki/Dependency_injection) to -enable easy mocking. If you define dependencies as interfaces rather than -concrete classes, you can swap out the production version of a class for a mock -during testing. - -You can also use gMock during the design phase for your system. By sketching -your architecture using mocks rather than full implementations, you can evolve -your design more quickly. - -## History and evolution - -In January 2007 Zhanyong Wan and the Testing Technology team met with -experienced C++ engineers to find out about C++ testing needs. The team learned -that creating mocks in C++ was a major pain point. They looked around for -existing frameworks but didn't find anything satisfactory. So Zhanyong Wan -tackled the problem of creating a usable C++ mocking framework. - -C++ posed a unique problem for mocking: while -[reflection](http://en.wikipedia.org/wiki/Reflection_\(computer_programming\)) -in Java and Python make it easy to generate a mock implementation of any -interface, C++ does not have reflection. Wan hit on macros as a way to simplify -mock writing in C++, and gMock was born. - -## Who to contact - -- g/gmock-users -- g/gmock-announce - -## Additional resources - -- [gMock](http://go/gmock) - homepage -- [GMock for Dummies](http://<!-- GOOGLETEST_CM0013 DO NOT DELETE -->) - gets you started with gMock - quickly -- [GMock Cookbook](http://<!-- GOOGLETEST_CM0012 DO NOT DELETE -->) - recipes for common scenarios; covers - advanced usage. -- [GMock Cheat Sheet](http://<!-- GOOGLETEST_CM0020 DO NOT DELETE -->) - a quick reference -- [GMock FAQ](http://<!-- GOOGLETEST_CM0021 DO NOT DELETE -->) - frequently asked questions -- [gUnit GDH page](http://go/gunit-overview) -- [gUnit User's Guide](http://goto.corp.google.com/gunit) - gets you started - with gUnit, which is closely related to gMock diff --git a/googlemock/docs/pump_manual.md b/googlemock/docs/pump_manual.md deleted file mode 100644 index 17fb370..0000000 --- a/googlemock/docs/pump_manual.md +++ /dev/null @@ -1,189 +0,0 @@ -<b>P</b>ump is <b>U</b>seful for <b>M</b>eta <b>P</b>rogramming. - -<!-- GOOGLETEST_CM0035 DO NOT DELETE --> - -# The Problem - -Template and macro libraries often need to define many classes, functions, or -macros that vary only (or almost only) in the number of arguments they take. -It's a lot of repetitive, mechanical, and error-prone work. - -Our experience is that it's tedious to write custom scripts, which tend to -reflect the structure of the generated code poorly and are often hard to read -and edit. For example, a small change needed in the generated code may require -some non-intuitive, non-trivial changes in the script. This is especially -painful when experimenting with the code. - -This script may be useful for generating meta code, for example a series of -macros of FOO1, FOO2, etc. Nevertheless, please make it your last resort -technique by favouring C++ template metaprogramming or variadic macros. - -# Our Solution - -Pump (for Pump is Useful for Meta Programming, Pretty Useful for Meta -Programming, or Practical Utility for Meta Programming, whichever you prefer) is -a simple meta-programming tool for C++. The idea is that a programmer writes a -`foo.pump` file which contains C++ code plus meta code that manipulates the C++ -code. The meta code can handle iterations over a range, nested iterations, local -meta variable definitions, simple arithmetic, and conditional expressions. You -can view it as a small Domain-Specific Language. The meta language is designed -to be non-intrusive (s.t. it won't confuse Emacs' C++ mode, for example) and -concise, making Pump code intuitive and easy to maintain. - -## Highlights - -* The implementation is in a single Python script and thus ultra portable: no - build or installation is needed and it works cross platforms. -* Pump tries to be smart with respect to - [Google's style guide](https://github.com/google/styleguide): it breaks long - lines (easy to have when they are generated) at acceptable places to fit - within 80 columns and indent the continuation lines correctly. -* The format is human-readable and more concise than XML. -* The format works relatively well with Emacs' C++ mode. - -## Examples - -The following Pump code (where meta keywords start with `$`, `[[` and `]]` are -meta brackets, and `$$` starts a meta comment that ends with the line): - -``` -$var n = 3 $$ Defines a meta variable n. -$range i 0..n $$ Declares the range of meta iterator i (inclusive). -$for i [[ - $$ Meta loop. -// Foo$i does blah for $i-ary predicates. -$range j 1..i -template <size_t N $for j [[, typename A$j]]> -class Foo$i { -$if i == 0 [[ - blah a; -]] $elif i <= 2 [[ - blah b; -]] $else [[ - blah c; -]] -}; - -]] -``` - -will be translated by the Pump compiler to: - -```cpp -// Foo0 does blah for 0-ary predicates. -template <size_t N> -class Foo0 { - blah a; -}; - -// Foo1 does blah for 1-ary predicates. -template <size_t N, typename A1> -class Foo1 { - blah b; -}; - -// Foo2 does blah for 2-ary predicates. -template <size_t N, typename A1, typename A2> -class Foo2 { - blah b; -}; - -// Foo3 does blah for 3-ary predicates. -template <size_t N, typename A1, typename A2, typename A3> -class Foo3 { - blah c; -}; -``` - -In another example, - -``` -$range i 1..n -Func($for i + [[a$i]]); -$$ The text between i and [[ is the separator between iterations. -``` - -will generate one of the following lines (without the comments), depending on -the value of `n`: - -```cpp -Func(); // If n is 0. -Func(a1); // If n is 1. -Func(a1 + a2); // If n is 2. -Func(a1 + a2 + a3); // If n is 3. -// And so on... -``` - -## Constructs - -We support the following meta programming constructs: - -| `$var id = exp` | Defines a named constant value. `$id` is | -: : valid until the end of the current meta : -: : lexical block. : -| :------------------------------- | :--------------------------------------- | -| `$range id exp..exp` | Sets the range of an iteration variable, | -: : which can be reused in multiple loops : -: : later. : -| `$for id sep [[ code ]]` | Iteration. The range of `id` must have | -: : been defined earlier. `$id` is valid in : -: : `code`. : -| `$($)` | Generates a single `$` character. | -| `$id` | Value of the named constant or iteration | -: : variable. : -| `$(exp)` | Value of the expression. | -| `$if exp [[ code ]] else_branch` | Conditional. | -| `[[ code ]]` | Meta lexical block. | -| `cpp_code` | Raw C++ code. | -| `$$ comment` | Meta comment. | - -**Note:** To give the user some freedom in formatting the Pump source code, Pump -ignores a new-line character if it's right after `$for foo` or next to `[[` or -`]]`. Without this rule you'll often be forced to write very long lines to get -the desired output. Therefore sometimes you may need to insert an extra new-line -in such places for a new-line to show up in your output. - -## Grammar - -```ebnf -code ::= atomic_code* -atomic_code ::= $var id = exp - | $var id = [[ code ]] - | $range id exp..exp - | $for id sep [[ code ]] - | $($) - | $id - | $(exp) - | $if exp [[ code ]] else_branch - | [[ code ]] - | cpp_code -sep ::= cpp_code | empty_string -else_branch ::= $else [[ code ]] - | $elif exp [[ code ]] else_branch - | empty_string -exp ::= simple_expression_in_Python_syntax -``` - -## Code - -You can find the source code of Pump in [scripts/pump.py](../scripts/pump.py). -It is still very unpolished and lacks automated tests, although it has been -successfully used many times. If you find a chance to use it in your project, -please let us know what you think! We also welcome help on improving Pump. - -## Real Examples - -You can find real-world applications of Pump in -[Google Test](https://github.com/google/googletest/tree/master/googletest) and -[Google Mock](https://github.com/google/googletest/tree/master/googlemock). The -source file `foo.h.pump` generates `foo.h`. - -## Tips - -* If a meta variable is followed by a letter or digit, you can separate them - using `[[]]`, which inserts an empty string. For example `Foo$j[[]]Helper` - generate `Foo1Helper` when `j` is 1. -* To avoid extra-long Pump source lines, you can break a line anywhere you - want by inserting `[[]]` followed by a new line. Since any new-line - character next to `[[` or `]]` is ignored, the generated code won't contain - this new line. diff --git a/googlemock/docs/sitemap.md b/googlemock/docs/sitemap.md deleted file mode 100644 index 78f2d1f..0000000 --- a/googlemock/docs/sitemap.md +++ /dev/null @@ -1,11 +0,0 @@ -Googletest Mocking (gMock) - -* [Home](index.md) -* [Overview](overview.md) -* [User's Guide](guide.md) -* [gMock For Dummies](for_dummies.md) -* [gMock Cookbook](cook_book.md) -* [gMock Cheat Sheet](cheat_sheet.md) -* [Design](design.md) -* [How To Contribute](contribute.md) -* [gMock FAQ](gmock_faq.md) diff --git a/googlemock/docs/under-construction-banner.md b/googlemock/docs/under-construction-banner.md deleted file mode 100644 index 2ee59f9..0000000 --- a/googlemock/docs/under-construction-banner.md +++ /dev/null @@ -1,4 +0,0 @@ -**WARNING:** This document was recently migrated from -[Goowiki](http://wtf/goowiki) (b/35424903) and may still require additional -updates or formatting. You can still access the original document on Goowiki -until the cleanup is complete: |