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diff --git a/googletest/docs/advanced.md b/googletest/docs/advanced.md new file mode 100644 index 0000000..feb8ad6 --- /dev/null +++ b/googletest/docs/advanced.md @@ -0,0 +1,2536 @@ +# Advanced googletest Topics + + +## Introduction + +Now that you have read the [googletest Primer](primer) and learned how to write +tests using googletest, it's time to learn some new tricks. This document will +show you more assertions as well as how to construct complex failure messages, +propagate fatal failures, reuse and speed up your test fixtures, and use various +flags with your tests. + +## More Assertions + +This section covers some less frequently used, but still significant, +assertions. + +### Explicit Success and Failure + +These three assertions do not actually test a value or expression. Instead, they +generate a success or failure directly. Like the macros that actually perform a +test, you may stream a custom failure message into them. + +```c++ +SUCCEED(); +``` + +Generates a success. This does **NOT** make the overall test succeed. A test is +considered successful only if none of its assertions fail during its execution. + +NOTE: `SUCCEED()` is purely documentary and currently doesn't generate any +user-visible output. However, we may add `SUCCEED()` messages to googletest's +output in the future. + +```c++ +FAIL(); +ADD_FAILURE(); +ADD_FAILURE_AT("file_path", line_number); +``` + +`FAIL()` generates a fatal failure, while `ADD_FAILURE()` and `ADD_FAILURE_AT()` +generate a nonfatal failure. These are useful when control flow, rather than a +Boolean expression, determines the test's success or failure. For example, you +might want to write something like: + +```c++ +switch(expression) { + case 1: + ... some checks ... + case 2: + ... some other checks ... + default: + FAIL() << "We shouldn't get here."; +} +``` + +NOTE: you can only use `FAIL()` in functions that return `void`. See the +[Assertion Placement section](#assertion-placement) for more information. + +**Availability**: Linux, Windows, Mac. + +### Exception Assertions + +These are for verifying that a piece of code throws (or does not throw) an +exception of the given type: + +Fatal assertion | Nonfatal assertion | Verifies +------------------------------------------ | ------------------------------------------ | -------- +`ASSERT_THROW(statement, exception_type);` | `EXPECT_THROW(statement, exception_type);` | `statement` throws an exception of the given type +`ASSERT_ANY_THROW(statement);` | `EXPECT_ANY_THROW(statement);` | `statement` throws an exception of any type +`ASSERT_NO_THROW(statement);` | `EXPECT_NO_THROW(statement);` | `statement` doesn't throw any exception + +Examples: + +```c++ +ASSERT_THROW(Foo(5), bar_exception); + +EXPECT_NO_THROW({ + int n = 5; + Bar(&n); +}); +``` + +**Availability**: Linux, Windows, Mac; requires exceptions to be enabled in the +build environment (note that `google3` **disables** exceptions). + +### Predicate Assertions for Better Error Messages + +Even though googletest has a rich set of assertions, they can never be complete, +as it's impossible (nor a good idea) to anticipate all scenarios a user might +run into. Therefore, sometimes a user has to use `EXPECT_TRUE()` to check a +complex expression, for lack of a better macro. This has the problem of not +showing you the values of the parts of the expression, making it hard to +understand what went wrong. As a workaround, some users choose to construct the +failure message by themselves, streaming it into `EXPECT_TRUE()`. However, this +is awkward especially when the expression has side-effects or is expensive to +evaluate. + +googletest gives you three different options to solve this problem: + +#### Using an Existing Boolean Function + +If you already have a function or functor that returns `bool` (or a type that +can be implicitly converted to `bool`), you can use it in a *predicate +assertion* to get the function arguments printed for free: + +| Fatal assertion | Nonfatal assertion | Verifies | +| -------------------- | -------------------- | --------------------------- | +| `ASSERT_PRED1(pred1, | `EXPECT_PRED1(pred1, | `pred1(val1)` is true | +: val1);` : val1);` : : +| `ASSERT_PRED2(pred2, | `EXPECT_PRED2(pred2, | `pred2(val1, val2)` is true | +: val1, val2);` : val1, val2);` : : +| `...` | `...` | ... | + +In the above, `predn` is an `n`-ary predicate function or functor, where `val1`, +`val2`, ..., and `valn` are its arguments. The assertion succeeds if the +predicate returns `true` when applied to the given arguments, and fails +otherwise. When the assertion fails, it prints the value of each argument. In +either case, the arguments are evaluated exactly once. + +Here's an example. Given + +```c++ +// Returns true iff m and n have no common divisors except 1. +bool MutuallyPrime(int m, int n) { ... } + +const int a = 3; +const int b = 4; +const int c = 10; +``` + +the assertion + +```c++ + EXPECT_PRED2(MutuallyPrime, a, b); +``` + +will succeed, while the assertion + +```c++ + EXPECT_PRED2(MutuallyPrime, b, c); +``` + +will fail with the message + +```none +MutuallyPrime(b, c) is false, where +b is 4 +c is 10 +``` + +> NOTE: +> +> 1. If you see a compiler error "no matching function to call" when using +> `ASSERT_PRED*` or `EXPECT_PRED*`, please see +> [this](faq#OverloadedPredicate) for how to resolve it. +> 1. Currently we only provide predicate assertions of arity <= 5. If you need +> a higher-arity assertion, let [us](https://github.com/google/googletest/issues) know. + +**Availability**: Linux, Windows, Mac. + +#### Using a Function That Returns an AssertionResult + +While `EXPECT_PRED*()` and friends are handy for a quick job, the syntax is not +satisfactory: you have to use different macros for different arities, and it +feels more like Lisp than C++. The `::testing::AssertionResult` class solves +this problem. + +An `AssertionResult` object represents the result of an assertion (whether it's +a success or a failure, and an associated message). You can create an +`AssertionResult` using one of these factory functions: + +```c++ +namespace testing { + +// Returns an AssertionResult object to indicate that an assertion has +// succeeded. +AssertionResult AssertionSuccess(); + +// Returns an AssertionResult object to indicate that an assertion has +// failed. +AssertionResult AssertionFailure(); + +} +``` + +You can then use the `<<` operator to stream messages to the `AssertionResult` +object. + +To provide more readable messages in Boolean assertions (e.g. `EXPECT_TRUE()`), +write a predicate function that returns `AssertionResult` instead of `bool`. For +example, if you define `IsEven()` as: + +```c++ +::testing::AssertionResult IsEven(int n) { + if ((n % 2) == 0) + return ::testing::AssertionSuccess(); + else + return ::testing::AssertionFailure() << n << " is odd"; +} +``` + +instead of: + +```c++ +bool IsEven(int n) { + return (n % 2) == 0; +} +``` + +the failed assertion `EXPECT_TRUE(IsEven(Fib(4)))` will print: + +```none +Value of: IsEven(Fib(4)) + Actual: false (3 is odd) +Expected: true +``` + +instead of a more opaque + +```none +Value of: IsEven(Fib(4)) + Actual: false +Expected: true +``` + +If you want informative messages in `EXPECT_FALSE` and `ASSERT_FALSE` as well +(one third of Boolean assertions in the Google code base are negative ones), and +are fine with making the predicate slower in the success case, you can supply a +success message: + +```c++ +::testing::AssertionResult IsEven(int n) { + if ((n % 2) == 0) + return ::testing::AssertionSuccess() << n << " is even"; + else + return ::testing::AssertionFailure() << n << " is odd"; +} +``` + +Then the statement `EXPECT_FALSE(IsEven(Fib(6)))` will print + +```none + Value of: IsEven(Fib(6)) + Actual: true (8 is even) + Expected: false +``` + +**Availability**: Linux, Windows, Mac. + +#### Using a Predicate-Formatter + +If you find the default message generated by `(ASSERT|EXPECT)_PRED*` and +`(ASSERT|EXPECT)_(TRUE|FALSE)` unsatisfactory, or some arguments to your +predicate do not support streaming to `ostream`, you can instead use the +following *predicate-formatter assertions* to *fully* customize how the message +is formatted: + +Fatal assertion | Nonfatal assertion | Verifies +------------------------------------------------ | ------------------------------------------------ | -------- +`ASSERT_PRED_FORMAT1(pred_format1, val1);` | `EXPECT_PRED_FORMAT1(pred_format1, val1);` | `pred_format1(val1)` is successful +`ASSERT_PRED_FORMAT2(pred_format2, val1, val2);` | `EXPECT_PRED_FORMAT2(pred_format2, val1, val2);` | `pred_format2(val1, val2)` is successful +`...` | `...` | ... + +The difference between this and the previous group of macros is that instead of +a predicate, `(ASSERT|EXPECT)_PRED_FORMAT*` take a *predicate-formatter* +(`pred_formatn`), which is a function or functor with the signature: + +```c++ +::testing::AssertionResult PredicateFormattern(const char* expr1, + const char* expr2, + ... + const char* exprn, + T1 val1, + T2 val2, + ... + Tn valn); +``` + +where `val1`, `val2`, ..., and `valn` are the values of the predicate arguments, +and `expr1`, `expr2`, ..., and `exprn` are the corresponding expressions as they +appear in the source code. The types `T1`, `T2`, ..., and `Tn` can be either +value types or reference types. For example, if an argument has type `Foo`, you +can declare it as either `Foo` or `const Foo&`, whichever is appropriate. + +As an example, let's improve the failure message in `MutuallyPrime()`, which was +used with `EXPECT_PRED2()`: + +```c++ +// Returns the smallest prime common divisor of m and n, +// or 1 when m and n are mutually prime. +int SmallestPrimeCommonDivisor(int m, int n) { ... } + +// A predicate-formatter for asserting that two integers are mutually prime. +::testing::AssertionResult AssertMutuallyPrime(const char* m_expr, + const char* n_expr, + int m, + int n) { + if (MutuallyPrime(m, n)) return ::testing::AssertionSuccess(); + + return ::testing::AssertionFailure() << m_expr << " and " << n_expr + << " (" << m << " and " << n << ") are not mutually prime, " + << "as they have a common divisor " << SmallestPrimeCommonDivisor(m, n); +} +``` + +With this predicate-formatter, we can use + +```c++ + EXPECT_PRED_FORMAT2(AssertMutuallyPrime, b, c); +``` + +to generate the message + +```none +b and c (4 and 10) are not mutually prime, as they have a common divisor 2. +``` + +As you may have realized, many of the built-in assertions we introduced earlier +are special cases of `(EXPECT|ASSERT)_PRED_FORMAT*`. In fact, most of them are +indeed defined using `(EXPECT|ASSERT)_PRED_FORMAT*`. + +**Availability**: Linux, Windows, Mac. + +### Floating-Point Comparison + +Comparing floating-point numbers is tricky. Due to round-off errors, it is very +unlikely that two floating-points will match exactly. Therefore, `ASSERT_EQ` 's +naive comparison usually doesn't work. And since floating-points can have a wide +value range, no single fixed error bound works. It's better to compare by a +fixed relative error bound, except for values close to 0 due to the loss of +precision there. + +In general, for floating-point comparison to make sense, the user needs to +carefully choose the error bound. If they don't want or care to, comparing in +terms of Units in the Last Place (ULPs) is a good default, and googletest +provides assertions to do this. Full details about ULPs are quite long; if you +want to learn more, see +[here](https://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/). + +#### Floating-Point Macros + +| Fatal assertion | Nonfatal assertion | Verifies | +| ----------------------- | ----------------------- | ----------------------- | +| `ASSERT_FLOAT_EQ(val1, | `EXPECT_FLOAT_EQ(val1, | the two `float` values | +: val2);` : val2);` : are almost equal : +| `ASSERT_DOUBLE_EQ(val1, | `EXPECT_DOUBLE_EQ(val1, | the two `double` values | +: val2);` : val2);` : are almost equal : + +By "almost equal" we mean the values are within 4 ULP's from each other. + +NOTE: `CHECK_DOUBLE_EQ()` in `base/logging.h` uses a fixed absolute error bound, +so its result may differ from that of the googletest macros. That macro is +unsafe and has been deprecated. Please don't use it any more. + +The following assertions allow you to choose the acceptable error bound: + +| Fatal assertion | Nonfatal assertion | Verifies | +| ------------------ | ------------------------ | ------------------------- | +| `ASSERT_NEAR(val1, | `EXPECT_NEAR(val1, val2, | the difference between | +: val2, abs_error);` : abs_error);` : `val1` and `val2` doesn't : +: : : exceed the given absolute : +: : : error : + +**Availability**: Linux, Windows, Mac. + +#### Floating-Point Predicate-Format Functions + +Some floating-point operations are useful, but not that often used. In order to +avoid an explosion of new macros, we provide them as predicate-format functions +that can be used in predicate assertion macros (e.g. `EXPECT_PRED_FORMAT2`, +etc). + +```c++ +EXPECT_PRED_FORMAT2(::testing::FloatLE, val1, val2); +EXPECT_PRED_FORMAT2(::testing::DoubleLE, val1, val2); +``` + +Verifies that `val1` is less than, or almost equal to, `val2`. You can replace +`EXPECT_PRED_FORMAT2` in the above table with `ASSERT_PRED_FORMAT2`. + +**Availability**: Linux, Windows, Mac. + +### Asserting Using gMock Matchers + +Google-developed C++ mocking framework [gMock](../../googlemock) comes with a +library of matchers for validating arguments passed to mock objects. A gMock +*matcher* is basically a predicate that knows how to describe itself. It can be +used in these assertion macros: + +| Fatal assertion | Nonfatal assertion | Verifies | +| ------------------- | ------------------------------ | --------------------- | +| `ASSERT_THAT(value, | `EXPECT_THAT(value, matcher);` | value matches matcher | +: matcher);` : : : + +For example, `StartsWith(prefix)` is a matcher that matches a string starting +with `prefix`, and you can write: + +```c++ +using ::testing::StartsWith; +... + // Verifies that Foo() returns a string starting with "Hello". + EXPECT_THAT(Foo(), StartsWith("Hello")); +``` + +Read this [recipe](../../googlemock/docs/CookBook.md#using-matchers-in-google-test-assertions) in +the gMock Cookbook for more details. + +gMock has a rich set of matchers. You can do many things googletest cannot do +alone with them. For a list of matchers gMock provides, read +[this](../../googlemock/docs/CookBook.md#using-matchers). Especially useful among them are +some [protocol buffer matchers](https://github.com/google/nucleus/blob/master/nucleus/testing/protocol-buffer-matchers.h). It's easy to write +your [own matchers](../../googlemock/docs/CookBook.md#writing-new-matchers-quickly) too. + +For example, you can use gMock's +[EqualsProto](https://github.com/google/nucleus/blob/master/nucleus/testing/protocol-buffer-matchers.h) +to compare protos in your tests: + +```c++ +#include "testing/base/public/gmock.h" +using ::testing::EqualsProto; +... + EXPECT_THAT(actual_proto, EqualsProto("foo: 123 bar: 'xyz'")); + EXPECT_THAT(*actual_proto_ptr, EqualsProto(expected_proto)); +``` + +gMock is bundled with googletest, so you don't need to add any build dependency +in order to take advantage of this. Just include `"testing/base/public/gmock.h"` +and you're ready to go. + +**Availability**: Linux, Windows, and Mac. + +### More String Assertions + +(Please read the [previous](#AssertThat) section first if you haven't.) + +You can use the gMock [string matchers](../../googlemock/docs/CheatSheet.md#string-matchers) +with `EXPECT_THAT()` or `ASSERT_THAT()` to do more string comparison tricks +(sub-string, prefix, suffix, regular expression, and etc). For example, + +```c++ +using ::testing::HasSubstr; +using ::testing::MatchesRegex; +... + ASSERT_THAT(foo_string, HasSubstr("needle")); + EXPECT_THAT(bar_string, MatchesRegex("\\w*\\d+")); +``` + +**Availability**: Linux, Windows, Mac. + +If the string contains a well-formed HTML or XML document, you can check whether +its DOM tree matches an [XPath +expression](http://www.w3.org/TR/xpath/#contents): + +```c++ +// Currently still in //template/prototemplate/testing:xpath_matcher +#include "template/prototemplate/testing/xpath_matcher.h" +using prototemplate::testing::MatchesXPath; +EXPECT_THAT(html_string, MatchesXPath("//a[text()='click here']")); +``` + +**Availability**: Linux. + +### Windows HRESULT assertions + +These assertions test for `HRESULT` success or failure. + +Fatal assertion | Nonfatal assertion | Verifies +-------------------------------------- | -------------------------------------- | -------- +`ASSERT_HRESULT_SUCCEEDED(expression)` | `EXPECT_HRESULT_SUCCEEDED(expression)` | `expression` is a success `HRESULT` +`ASSERT_HRESULT_FAILED(expression)` | `EXPECT_HRESULT_FAILED(expression)` | `expression` is a failure `HRESULT` + +The generated output contains the human-readable error message associated with +the `HRESULT` code returned by `expression`. + +You might use them like this: + +```c++ +CComPtr<IShellDispatch2> shell; +ASSERT_HRESULT_SUCCEEDED(shell.CoCreateInstance(L"Shell.Application")); +CComVariant empty; +ASSERT_HRESULT_SUCCEEDED(shell->ShellExecute(CComBSTR(url), empty, empty, empty, empty)); +``` + +**Availability**: Windows. + +### Type Assertions + +You can call the function + +```c++ +::testing::StaticAssertTypeEq<T1, T2>(); +``` + +to assert that types `T1` and `T2` are the same. The function does nothing if +the assertion is satisfied. If the types are different, the function call will +fail to compile, and the compiler error message will likely (depending on the +compiler) show you the actual values of `T1` and `T2`. This is mainly useful +inside template code. + +**Caveat**: When used inside a member function of a class template or a function +template, `StaticAssertTypeEq<T1, T2>()` is effective only if the function is +instantiated. For example, given: + +```c++ +template <typename T> class Foo { + public: + void Bar() { ::testing::StaticAssertTypeEq<int, T>(); } +}; +``` + +the code: + +```c++ +void Test1() { Foo<bool> foo; } +``` + +will not generate a compiler error, as `Foo<bool>::Bar()` is never actually +instantiated. Instead, you need: + +```c++ +void Test2() { Foo<bool> foo; foo.Bar(); } +``` + +to cause a compiler error. + +**Availability**: Linux, Windows, Mac. + +### Assertion Placement + +You can use assertions in any C++ function. In particular, it doesn't have to be +a method of the test fixture class. The one constraint is that assertions that +generate a fatal failure (`FAIL*` and `ASSERT_*`) can only be used in +void-returning functions. This is a consequence of Google's not using +exceptions. By placing it in a non-void function you'll get a confusing compile +error like `"error: void value not ignored as it ought to be"` or `"cannot +initialize return object of type 'bool' with an rvalue of type 'void'"` or +`"error: no viable conversion from 'void' to 'string'"`. + +If you need to use fatal assertions in a function that returns non-void, one +option is to make the function return the value in an out parameter instead. For +example, you can rewrite `T2 Foo(T1 x)` to `void Foo(T1 x, T2* result)`. You +need to make sure that `*result` contains some sensible value even when the +function returns prematurely. As the function now returns `void`, you can use +any assertion inside of it. + +If changing the function's type is not an option, you should just use assertions +that generate non-fatal failures, such as `ADD_FAILURE*` and `EXPECT_*`. + +NOTE: Constructors and destructors are not considered void-returning functions, +according to the C++ language specification, and so you may not use fatal +assertions in them. You'll get a compilation error if you try. A simple +workaround is to transfer the entire body of the constructor or destructor to a +private void-returning method. However, you should be aware that a fatal +assertion failure in a constructor does not terminate the current test, as your +intuition might suggest; it merely returns from the constructor early, possibly +leaving your object in a partially-constructed state. Likewise, a fatal +assertion failure in a destructor may leave your object in a +partially-destructed state. Use assertions carefully in these situations! + +## Teaching googletest How to Print Your Values + +When a test assertion such as `EXPECT_EQ` fails, googletest prints the argument +values to help you debug. It does this using a 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. + +As mentioned earlier, the printer is *extensible*. That means you can teach it +to do a better job at printing your particular type than to dump the bytes. To +do that, define `<<` for your type: + +```c++ +// Streams are allowed only for logging. Don't include this for +// any other purpose. +#include <ostream> + +namespace foo { + +class Bar { // We want googletest to be able to print instances of this. +... + // Create a free inline friend function. + friend ::std::ostream& operator<<(::std::ostream& os, const Bar& bar) { + return os << bar.DebugString(); // whatever needed to print bar to os + } +}; + +// If you can't declare the function in the class it's important that the +// << operator is defined in the SAME namespace that defines Bar. C++'s look-up +// rules rely on that. +::std::ostream& operator<<(::std::ostream& os, const Bar& bar) { + return os << bar.DebugString(); // whatever needed to print bar to os +} + +} // namespace foo +``` + +Sometimes, this might not be an option: your team may consider it bad style to +have a `<<` operator for `Bar`, or `Bar` may already have a `<<` operator that +doesn't do what you want (and you cannot change it). If so, you can instead +define a `PrintTo()` function like this: + +```c++ +// Streams are allowed only for logging. Don't include this for +// any other purpose. +#include <ostream> + +namespace foo { + +class Bar { + ... + friend void PrintTo(const Bar& bar, ::std::ostream* os) { + *os << bar.DebugString(); // whatever needed to print bar to os + } +}; + +// If you can't declare the function in the class it's important that PrintTo() +// is defined in the SAME namespace that defines Bar. C++'s look-up rules rely +// on that. +void PrintTo(const Bar& bar, ::std::ostream* os) { + *os << bar.DebugString(); // whatever needed to print bar to os +} + +} // namespace foo +``` + +If you have defined both `<<` and `PrintTo()`, the latter will be used when +googletest is concerned. This allows you to customize how the value appears in +googletest's output without affecting code that relies on the behavior of its +`<<` operator. + +If you want to print a value `x` using googletest's value printer yourself, just +call `::testing::PrintToString(x)`, which returns an `std::string`: + +```c++ +vector<pair<Bar, int> > bar_ints = GetBarIntVector(); + +EXPECT_TRUE(IsCorrectBarIntVector(bar_ints)) + << "bar_ints = " << ::testing::PrintToString(bar_ints); +``` + +## Death Tests + +In many applications, there are assertions that can cause application failure if +a condition is not met. These sanity checks, which ensure that the program is in +a known good state, are there to fail at the earliest possible time after some +program state is corrupted. If the assertion checks the wrong condition, then +the program may proceed in an erroneous state, which could lead to memory +corruption, security holes, or worse. Hence it is vitally important to test that +such assertion statements work as expected. + +Since these precondition checks cause the processes to die, we call such tests +_death tests_. More generally, any test that checks that a program terminates +(except by throwing an exception) in an expected fashion is also a death test. + + +Note that if a piece of code throws an exception, we don't consider it "death" +for the purpose of death tests, as the caller of the code could catch the +exception and avoid the crash. If you want to verify exceptions thrown by your +code, see [Exception Assertions](#ExceptionAssertions). + +If you want to test `EXPECT_*()/ASSERT_*()` failures in your test code, see +Catching Failures + +### How to Write a Death Test + +googletest has the following macros to support death tests: + +Fatal assertion | Nonfatal assertion | Verifies +---------------------------------------------- | ---------------------------------------------- | -------- +`ASSERT_DEATH(statement, regex);` | `EXPECT_DEATH(statement, regex);` | `statement` crashes with the given error +`ASSERT_DEATH_IF_SUPPORTED(statement, regex);` | `EXPECT_DEATH_IF_SUPPORTED(statement, regex);` | if death tests are supported, verifies that `statement` crashes with the given error; otherwise verifies nothing +`ASSERT_EXIT(statement, predicate, regex);` | `EXPECT_EXIT(statement, predicate, regex);` | `statement` exits with the given error, and its exit code matches `predicate` + +where `statement` is a statement that is expected to cause the process to die, +`predicate` is a function or function object that evaluates an integer exit +status, and `regex` is a (Perl) regular expression that the stderr output of +`statement` is expected to match. Note that `statement` can be *any valid +statement* (including *compound statement*) and doesn't have to be an +expression. + + +As usual, the `ASSERT` variants abort the current test function, while the +`EXPECT` variants do not. + +> NOTE: We use the word "crash" here to mean that the process terminates with a +> *non-zero* exit status code. There are two possibilities: either the process +> has called `exit()` or `_exit()` with a non-zero value, or it may be killed by +> a signal. +> +> This means that if `*statement*` terminates the process with a 0 exit code, it +> is *not* considered a crash by `EXPECT_DEATH`. Use `EXPECT_EXIT` instead if +> this is the case, or if you want to restrict the exit code more precisely. + +A predicate here must accept an `int` and return a `bool`. The death test +succeeds only if the predicate returns `true`. googletest defines a few +predicates that handle the most common cases: + +```c++ +::testing::ExitedWithCode(exit_code) +``` + +This expression is `true` if the program exited normally with the given exit +code. + +```c++ +::testing::KilledBySignal(signal_number) // Not available on Windows. +``` + +This expression is `true` if the program was killed by the given signal. + +The `*_DEATH` macros are convenient wrappers for `*_EXIT` that use a predicate +that verifies the process' exit code is non-zero. + +Note that a death test only cares about three things: + +1. does `statement` abort or exit the process? +2. (in the case of `ASSERT_EXIT` and `EXPECT_EXIT`) does the exit status + satisfy `predicate`? Or (in the case of `ASSERT_DEATH` and `EXPECT_DEATH`) + is the exit status non-zero? And +3. does the stderr output match `regex`? + +In particular, if `statement` generates an `ASSERT_*` or `EXPECT_*` failure, it +will **not** cause the death test to fail, as googletest assertions don't abort +the process. + +To write a death test, simply use one of the above macros inside your test +function. For example, + +```c++ +TEST(MyDeathTest, Foo) { + // This death test uses a compound statement. + ASSERT_DEATH({ + int n = 5; + Foo(&n); + }, "Error on line .* of Foo()"); +} + +TEST(MyDeathTest, NormalExit) { + EXPECT_EXIT(NormalExit(), ::testing::ExitedWithCode(0), "Success"); +} + +TEST(MyDeathTest, KillMyself) { + EXPECT_EXIT(KillMyself(), ::testing::KilledBySignal(SIGKILL), + "Sending myself unblockable signal"); +} +``` + +verifies that: + +* calling `Foo(5)` causes the process to die with the given error message, +* calling `NormalExit()` causes the process to print `"Success"` to stderr and + exit with exit code 0, and +* calling `KillMyself()` kills the process with signal `SIGKILL`. + +The test function body may contain other assertions and statements as well, if +necessary. + +### Death Test Naming + +IMPORTANT: We strongly recommend you to follow the convention of naming your +**test case** (not test) `*DeathTest` when it contains a death test, as +demonstrated in the above example. The [Death Tests And +Threads](#death-tests-and-threads) section below explains why. + +If a test fixture class is shared by normal tests and death tests, you can use +`using` or `typedef` to introduce an alias for the fixture class and avoid +duplicating its code: + +```c++ +class FooTest : public ::testing::Test { ... }; + +using FooDeathTest = FooTest; + +TEST_F(FooTest, DoesThis) { + // normal test +} + +TEST_F(FooDeathTest, DoesThat) { + // death test +} +``` + +**Availability**: Linux, Windows (requires MSVC 8.0 or above), Cygwin, and Mac + +### Regular Expression Syntax + + +On POSIX systems (e.g. Linux, Cygwin, and Mac), googletest uses the +[POSIX extended regular expression](http://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap09.html#tag_09_04) +syntax. To learn about this syntax, you may want to read this +[Wikipedia entry](http://en.wikipedia.org/wiki/Regular_expression#POSIX_Extended_Regular_Expressions). + +On Windows, googletest uses its own simple regular expression implementation. It +lacks many features. For example, we don't support union (`"x|y"`), grouping +(`"(xy)"`), brackets (`"[xy]"`), and repetition count (`"x{5,7}"`), among +others. Below is what we do support (`A` denotes a literal character, period +(`.`), or a single `\\ ` escape sequence; `x` and `y` denote regular +expressions.): + +Expression | Meaning +---------- | -------------------------------------------------------------- +`c` | matches any literal character `c` +`\\d` | matches any decimal digit +`\\D` | matches any character that's not a decimal digit +`\\f` | matches `\f` +`\\n` | matches `\n` +`\\r` | matches `\r` +`\\s` | matches any ASCII whitespace, including `\n` +`\\S` | matches any character that's not a whitespace +`\\t` | matches `\t` +`\\v` | matches `\v` +`\\w` | matches any letter, `_`, or decimal digit +`\\W` | matches any character that `\\w` doesn't match +`\\c` | matches any literal character `c`, which must be a punctuation +`.` | matches any single character except `\n` +`A?` | matches 0 or 1 occurrences of `A` +`A*` | matches 0 or many occurrences of `A` +`A+` | matches 1 or many occurrences of `A` +`^` | matches the beginning of a string (not that of each line) +`$` | matches the end of a string (not that of each line) +`xy` | matches `x` followed by `y` + +To help you determine which capability is available on your system, googletest +defines macros to govern which regular expression it is using. The macros are: +<!--absl:google3-begin(google3-only)-->`GTEST_USES_PCRE=1`, or +<!--absl:google3-end--> `GTEST_USES_SIMPLE_RE=1` or `GTEST_USES_POSIX_RE=1`. If +you want your death tests to work in all cases, you can either `#if` on these +macros or use the more limited syntax only. + +### How It Works + +Under the hood, `ASSERT_EXIT()` spawns a new process and executes the death test +statement in that process. The details of how precisely that happens depend on +the platform and the variable ::testing::GTEST_FLAG(death_test_style) (which is +initialized from the command-line flag `--gtest_death_test_style`). + +* On POSIX systems, `fork()` (or `clone()` on Linux) is used to spawn the + child, after which: + * If the variable's value is `"fast"`, the death test statement is + immediately executed. + * If the variable's value is `"threadsafe"`, the child process re-executes + the unit test binary just as it was originally invoked, but with some + extra flags to cause just the single death test under consideration to + be run. +* On Windows, the child is spawned using the `CreateProcess()` API, and + re-executes the binary to cause just the single death test under + consideration to be run - much like the `threadsafe` mode on POSIX. + +Other values for the variable are illegal and will cause the death test to fail. +Currently, the flag's default value is +"fast". However, we reserve +the right to change it in the future. Therefore, your tests should not depend on +this. In either case, the parent process waits for the child process to +complete, and checks that + +1. the child's exit status satisfies the predicate, and +2. the child's stderr matches the regular expression. + +If the death test statement runs to completion without dying, the child process +will nonetheless terminate, and the assertion fails. + +### Death Tests And Threads + +The reason for the two death test styles has to do with thread safety. Due to +well-known problems with forking in the presence of threads, death tests should +be run in a single-threaded context. Sometimes, however, it isn't feasible to +arrange that kind of environment. For example, statically-initialized modules +may start threads before main is ever reached. Once threads have been created, +it may be difficult or impossible to clean them up. + +googletest has three features intended to raise awareness of threading issues. + +1. A warning is emitted if multiple threads are running when a death test is + encountered. +2. Test cases with a name ending in "DeathTest" are run before all other tests. +3. It uses `clone()` instead of `fork()` to spawn the child process on Linux + (`clone()` is not available on Cygwin and Mac), as `fork()` is more likely + to cause the child to hang when the parent process has multiple threads. + +It's perfectly fine to create threads inside a death test statement; they are +executed in a separate process and cannot affect the parent. + +### Death Test Styles + + +The "threadsafe" death test style was introduced in order to help mitigate the +risks of testing in a possibly multithreaded environment. It trades increased +test execution time (potentially dramatically so) for improved thread safety. + +The automated testing framework does not set the style flag. You can choose a +particular style of death tests by setting the flag programmatically: + +```c++ +testing::FLAGS_gtest_death_test_style="threadsafe" +``` + +You can do this in `main()` to set the style for all death tests in the binary, +or in individual tests. Recall that flags are saved before running each test and +restored afterwards, so you need not do that yourself. For example: + +```c++ +int main(int argc, char** argv) { + InitGoogle(argv[0], &argc, &argv, true); + ::testing::FLAGS_gtest_death_test_style = "fast"; + return RUN_ALL_TESTS(); +} + +TEST(MyDeathTest, TestOne) { + ::testing::FLAGS_gtest_death_test_style = "threadsafe"; + // This test is run in the "threadsafe" style: + ASSERT_DEATH(ThisShouldDie(), ""); +} + +TEST(MyDeathTest, TestTwo) { + // This test is run in the "fast" style: + ASSERT_DEATH(ThisShouldDie(), ""); +} +``` + + +### Caveats + +The `statement` argument of `ASSERT_EXIT()` can be any valid C++ statement. If +it leaves the current function via a `return` statement or by throwing an +exception, the death test is considered to have failed. Some googletest macros +may return from the current function (e.g. `ASSERT_TRUE()`), so be sure to avoid +them in `statement`. + +Since `statement` runs in the child process, any in-memory side effect (e.g. +modifying a variable, releasing memory, etc) it causes will *not* be observable +in the parent process. In particular, if you release memory in a death test, +your program will fail the heap check as the parent process will never see the +memory reclaimed. To solve this problem, you can + +1. try not to free memory in a death test; +2. free the memory again in the parent process; or +3. do not use the heap checker in your program. + +Due to an implementation detail, you cannot place multiple death test assertions +on the same line; otherwise, compilation will fail with an unobvious error +message. + +Despite the improved thread safety afforded by the "threadsafe" style of death +test, thread problems such as deadlock are still possible in the presence of +handlers registered with `pthread_atfork(3)`. + + +## Using Assertions in Sub-routines + +### Adding Traces to Assertions + +If a test sub-routine is called from several places, when an assertion inside it +fails, it can be hard to tell which invocation of the sub-routine the failure is +from. +You can alleviate this problem using extra logging or custom failure messages, +but that usually clutters up your tests. A better solution is to use the +`SCOPED_TRACE` macro or the `ScopedTrace` utility: + +```c++ +SCOPED_TRACE(message); +ScopedTrace trace("file_path", line_number, message); +``` + +where `message` can be anything streamable to `std::ostream`. `SCOPED_TRACE` +macro will cause the current file name, line number, and the given message to be +added in every failure message. `ScopedTrace` accepts explicit file name and +line number in arguments, which is useful for writing test helpers. The effect +will be undone when the control leaves the current lexical scope. + +For example, + +```c++ +10: void Sub1(int n) { +11: EXPECT_EQ(1, Bar(n)); +12: EXPECT_EQ(2, Bar(n + 1)); +13: } +14: +15: TEST(FooTest, Bar) { +16: { +17: SCOPED_TRACE("A"); // This trace point will be included in +18: // every failure in this scope. +19: Sub1(1); +20: } +21: // Now it won't. +22: Sub1(9); +23: } +``` + +could result in messages like these: + +```none +path/to/foo_test.cc:11: Failure +Value of: Bar(n) +Expected: 1 + Actual: 2 + Trace: +path/to/foo_test.cc:17: A + +path/to/foo_test.cc:12: Failure +Value of: Bar(n + 1) +Expected: 2 + Actual: 3 +``` + +Without the trace, it would've been difficult to know which invocation of +`Sub1()` the two failures come from respectively. (You could add + +an extra message to each assertion in `Sub1()` to indicate the value of `n`, but +that's tedious.) + +Some tips on using `SCOPED_TRACE`: + +1. With a suitable message, it's often enough to use `SCOPED_TRACE` at the + beginning of a sub-routine, instead of at each call site. +2. When calling sub-routines inside a loop, make the loop iterator part of the + message in `SCOPED_TRACE` such that you can know which iteration the failure + is from. +3. Sometimes the line number of the trace point is enough for identifying the + particular invocation of a sub-routine. In this case, you don't have to + choose a unique message for `SCOPED_TRACE`. You can simply use `""`. +4. You can use `SCOPED_TRACE` in an inner scope when there is one in the outer + scope. In this case, all active trace points will be included in the failure + messages, in reverse order they are encountered. +5. The trace dump is clickable in Emacs - hit `return` on a line number and + you'll be taken to that line in the source file! + +**Availability**: Linux, Windows, Mac. + +### Propagating Fatal Failures + +A common pitfall when using `ASSERT_*` and `FAIL*` is not understanding that +when they fail they only abort the _current function_, not the entire test. For +example, the following test will segfault: + +```c++ +void Subroutine() { + // Generates a fatal failure and aborts the current function. + ASSERT_EQ(1, 2); + + // The following won't be executed. + ... +} + +TEST(FooTest, Bar) { + Subroutine(); // The intended behavior is for the fatal failure + // in Subroutine() to abort the entire test. + + // The actual behavior: the function goes on after Subroutine() returns. + int* p = NULL; + *p = 3; // Segfault! +} +``` + +To alleviate this, googletest provides three different solutions. You could use +either exceptions, the `(ASSERT|EXPECT)_NO_FATAL_FAILURE` assertions or the +`HasFatalFailure()` function. They are described in the following two +subsections. + +#### Asserting on Subroutines with an exception + +The following code can turn ASSERT-failure into an exception: + +```c++ +class ThrowListener : public testing::EmptyTestEventListener { + void OnTestPartResult(const testing::TestPartResult& result) override { + if (result.type() == testing::TestPartResult::kFatalFailure) { + throw testing::AssertionException(result); + } + } +}; +int main(int argc, char** argv) { + ... + testing::UnitTest::GetInstance()->listeners().Append(new ThrowListener); + return RUN_ALL_TESTS(); +} +``` + +This listener should be added after other listeners if you have any, otherwise +they won't see failed `OnTestPartResult`. + +#### Asserting on Subroutines + +As shown above, if your test calls a subroutine that has an `ASSERT_*` failure +in it, the test will continue after the subroutine returns. This may not be what +you want. + +Often people want fatal failures to propagate like exceptions. For that +googletest offers the following macros: + +Fatal assertion | Nonfatal assertion | Verifies +------------------------------------- | ------------------------------------- | -------- +`ASSERT_NO_FATAL_FAILURE(statement);` | `EXPECT_NO_FATAL_FAILURE(statement);` | `statement` doesn't generate any new fatal failures in the current thread. + +Only failures in the thread that executes the assertion are checked to determine +the result of this type of assertions. If `statement` creates new threads, +failures in these threads are ignored. + +Examples: + +```c++ +ASSERT_NO_FATAL_FAILURE(Foo()); + +int i; +EXPECT_NO_FATAL_FAILURE({ + i = Bar(); +}); +``` + +**Availability**: Linux, Windows, Mac. Assertions from multiple threads are +currently not supported on Windows. + +#### Checking for Failures in the Current Test + +`HasFatalFailure()` in the `::testing::Test` class returns `true` if an +assertion in the current test has suffered a fatal failure. This allows +functions to catch fatal failures in a sub-routine and return early. + +```c++ +class Test { + public: + ... + static bool HasFatalFailure(); +}; +``` + +The typical usage, which basically simulates the behavior of a thrown exception, +is: + +```c++ +TEST(FooTest, Bar) { + Subroutine(); + // Aborts if Subroutine() had a fatal failure. + if (HasFatalFailure()) return; + + // The following won't be executed. + ... +} +``` + +If `HasFatalFailure()` is used outside of `TEST()` , `TEST_F()` , or a test +fixture, you must add the `::testing::Test::` prefix, as in: + +```c++ +if (::testing::Test::HasFatalFailure()) return; +``` + +Similarly, `HasNonfatalFailure()` returns `true` if the current test has at +least one non-fatal failure, and `HasFailure()` returns `true` if the current +test has at least one failure of either kind. + +**Availability**: Linux, Windows, Mac. + +## Logging Additional Information + +In your test code, you can call `RecordProperty("key", value)` to log additional +information, where `value` can be either a string or an `int`. The *last* value +recorded for a key will be emitted to the [XML output](#XmlReport) if you +specify one. For example, the test + +```c++ +TEST_F(WidgetUsageTest, MinAndMaxWidgets) { + RecordProperty("MaximumWidgets", ComputeMaxUsage()); + RecordProperty("MinimumWidgets", ComputeMinUsage()); +} +``` + +will output XML like this: + +```xml + ... + <testcase name="MinAndMaxWidgets" status="run" time="0.006" classname="WidgetUsageTest" MaximumWidgets="12" MinimumWidgets="9" /> + ... +``` + +> NOTE: +> +> * `RecordProperty()` is a static member of the `Test` class. Therefore it +> needs to be prefixed with `::testing::Test::` if used outside of the +> `TEST` body and the test fixture class. +> * `*key*` must be a valid XML attribute name, and cannot conflict with the +> ones already used by googletest (`name`, `status`, `time`, `classname`, +> `type_param`, and `value_param`). +> * Calling `RecordProperty()` outside of the lifespan of a test is allowed. +> If it's called outside of a test but between a test case's +> `SetUpTestCase()` and `TearDownTestCase()` methods, it will be attributed +> to the XML element for the test case. If it's called outside of all test +> cases (e.g. in a test environment), it will be attributed to the top-level +> XML element. + +**Availability**: Linux, Windows, Mac. + +## Sharing Resources Between Tests in the Same Test Case + +googletest creates a new test fixture object for each test in order to make +tests independent and easier to debug. However, sometimes tests use resources +that are expensive to set up, making the one-copy-per-test model prohibitively +expensive. + +If the tests don't change the resource, there's no harm in their sharing a +single resource copy. So, in addition to per-test set-up/tear-down, googletest +also supports per-test-case set-up/tear-down. To use it: + +1. In your test fixture class (say `FooTest` ), declare as `static` some member + variables to hold the shared resources. +1. Outside your test fixture class (typically just below it), define those + member variables, optionally giving them initial values. +1. In the same test fixture class, define a `static void SetUpTestCase()` + function (remember not to spell it as **`SetupTestCase`** with a small `u`!) + to set up the shared resources and a `static void TearDownTestCase()` + function to tear them down. + +That's it! googletest automatically calls `SetUpTestCase()` before running the +*first test* in the `FooTest` test case (i.e. before creating the first +`FooTest` object), and calls `TearDownTestCase()` after running the *last test* +in it (i.e. after deleting the last `FooTest` object). In between, the tests can +use the shared resources. + +Remember that the test order is undefined, so your code can't depend on a test +preceding or following another. Also, the tests must either not modify the state +of any shared resource, or, if they do modify the state, they must restore the +state to its original value before passing control to the next test. + +Here's an example of per-test-case set-up and tear-down: + +```c++ +class FooTest : public ::testing::Test { + protected: + // Per-test-case set-up. + // Called before the first test in this test case. + // Can be omitted if not needed. + static void SetUpTestCase() { + shared_resource_ = new ...; + } + + // Per-test-case tear-down. + // Called after the last test in this test case. + // Can be omitted if not needed. + static void TearDownTestCase() { + delete shared_resource_; + shared_resource_ = NULL; + } + + // You can define per-test set-up logic as usual. + virtual void SetUp() { ... } + + // You can define per-test tear-down logic as usual. + virtual void TearDown() { ... } + + // Some expensive resource shared by all tests. + static T* shared_resource_; +}; + +T* FooTest::shared_resource_ = NULL; + +TEST_F(FooTest, Test1) { + ... you can refer to shared_resource_ here ... +} + +TEST_F(FooTest, Test2) { + ... you can refer to shared_resource_ here ... +} +``` + +NOTE: Though the above code declares `SetUpTestCase()` protected, it may +sometimes be necessary to declare it public, such as when using it with +`TEST_P`. + +**Availability**: Linux, Windows, Mac. + +## Global Set-Up and Tear-Down + +Just as you can do set-up and tear-down at the test level and the test case +level, you can also do it at the test program level. Here's how. + +First, you subclass the `::testing::Environment` class to define a test +environment, which knows how to set-up and tear-down: + +```c++ +class Environment { + public: + virtual ~Environment() {} + + // Override this to define how to set up the environment. + virtual void SetUp() {} + + // Override this to define how to tear down the environment. + virtual void TearDown() {} +}; +``` + +Then, you register an instance of your environment class with googletest by +calling the `::testing::AddGlobalTestEnvironment()` function: + +```c++ +Environment* AddGlobalTestEnvironment(Environment* env); +``` + +Now, when `RUN_ALL_TESTS()` is called, it first calls the `SetUp()` method of +the environment object, then runs the tests if there was no fatal failures, and +finally calls `TearDown()` of the environment object. + +It's OK to register multiple environment objects. In this case, their `SetUp()` +will be called in the order they are registered, and their `TearDown()` will be +called in the reverse order. + +Note that googletest takes ownership of the registered environment objects. +Therefore **do not delete them** by yourself. + +You should call `AddGlobalTestEnvironment()` before `RUN_ALL_TESTS()` is called, +probably in `main()`. If you use `gtest_main`, you need to call this before +`main()` starts for it to take effect. One way to do this is to define a global +variable like this: + +```c++ +::testing::Environment* const foo_env = + ::testing::AddGlobalTestEnvironment(new FooEnvironment); +``` + +However, we strongly recommend you to write your own `main()` and call +`AddGlobalTestEnvironment()` there, as relying on initialization of global +variables makes the code harder to read and may cause problems when you register +multiple environments from different translation units and the environments have +dependencies among them (remember that the compiler doesn't guarantee the order +in which global variables from different translation units are initialized). + +## Value-Parameterized Tests + +*Value-parameterized tests* allow you to test your code with different +parameters without writing multiple copies of the same test. This is useful in a +number of situations, for example: + +* You have a piece of code whose behavior is affected by one or more + command-line flags. You want to make sure your code performs correctly for + various values of those flags. +* You want to test different implementations of an OO interface. +* You want to test your code over various inputs (a.k.a. data-driven testing). + This feature is easy to abuse, so please exercise your good sense when doing + it! + +### How to Write Value-Parameterized Tests + +To write value-parameterized tests, first you should define a fixture class. It +must be derived from both `::testing::Test` and +`::testing::WithParamInterface<T>` (the latter is a pure interface), where `T` +is the type of your parameter values. For convenience, you can just derive the +fixture class from `::testing::TestWithParam<T>`, which itself is derived from +both `::testing::Test` and `::testing::WithParamInterface<T>`. `T` can be any +copyable type. If it's a raw pointer, you are responsible for managing the +lifespan of the pointed values. + +NOTE: If your test fixture defines `SetUpTestCase()` or `TearDownTestCase()` +they must be declared **public** rather than **protected** in order to use +`TEST_P`. + +```c++ +class FooTest : + public ::testing::TestWithParam<const char*> { + // You can implement all the usual fixture class members here. + // To access the test parameter, call GetParam() from class + // TestWithParam<T>. +}; + +// Or, when you want to add parameters to a pre-existing fixture class: +class BaseTest : public ::testing::Test { + ... +}; +class BarTest : public BaseTest, + public ::testing::WithParamInterface<const char*> { + ... +}; +``` + +Then, use the `TEST_P` macro to define as many test patterns using this fixture +as you want. The `_P` suffix is for "parameterized" or "pattern", whichever you +prefer to think. + +```c++ +TEST_P(FooTest, DoesBlah) { + // Inside a test, access the test parameter with the GetParam() method + // of the TestWithParam<T> class: + EXPECT_TRUE(foo.Blah(GetParam())); + ... +} + +TEST_P(FooTest, HasBlahBlah) { + ... +} +``` + +Finally, you can use `INSTANTIATE_TEST_CASE_P` to instantiate the test case with +any set of parameters you want. googletest defines a number of functions for +generating test parameters. They return what we call (surprise!) *parameter +generators*. Here is a summary of them, which are all in the `testing` +namespace: + +| Parameter Generator | Behavior | +| ---------------------------- | ------------------------------------------- | +| `Range(begin, end [, step])` | Yields values `{begin, begin+step, | +: : begin+step+step, ...}`. The values do not : +: : include `end`. `step` defaults to 1. : +| `Values(v1, v2, ..., vN)` | Yields values `{v1, v2, ..., vN}`. | +| `ValuesIn(container)` and | Yields values from a C-style array, an | +: `ValuesIn(begin,end)` : STL-style container, or an iterator range : +: : `[begin, end)`. : +| `Bool()` | Yields sequence `{false, true}`. | +| `Combine(g1, g2, ..., gN)` | Yields all combinations (Cartesian product) | +: : as std\:\:tuples of the values generated by : +: : the `N` generators. : + +For more details, see the comments at the definitions of these functions. + +The following statement will instantiate tests from the `FooTest` test case each +with parameter values `"meeny"`, `"miny"`, and `"moe"`. + +```c++ +INSTANTIATE_TEST_CASE_P(InstantiationName, + FooTest, + ::testing::Values("meeny", "miny", "moe")); +``` + +NOTE: The code above must be placed at global or namespace scope, not at +function scope. + +NOTE: Don't forget this step! If you do your test will silently pass, but none +of its cases will ever run! + +To distinguish different instances of the pattern (yes, you can instantiate it +more than once), the first argument to `INSTANTIATE_TEST_CASE_P` is a prefix +that will be added to the actual test case name. Remember to pick unique +prefixes for different instantiations. The tests from the instantiation above +will have these names: + +* `InstantiationName/FooTest.DoesBlah/0` for `"meeny"` +* `InstantiationName/FooTest.DoesBlah/1` for `"miny"` +* `InstantiationName/FooTest.DoesBlah/2` for `"moe"` +* `InstantiationName/FooTest.HasBlahBlah/0` for `"meeny"` +* `InstantiationName/FooTest.HasBlahBlah/1` for `"miny"` +* `InstantiationName/FooTest.HasBlahBlah/2` for `"moe"` + +You can use these names in [`--gtest_filter`](#TestFilter). + +This statement will instantiate all tests from `FooTest` again, each with +parameter values `"cat"` and `"dog"`: + +```c++ +const char* pets[] = {"cat", "dog"}; +INSTANTIATE_TEST_CASE_P(AnotherInstantiationName, FooTest, + ::testing::ValuesIn(pets)); +``` + +The tests from the instantiation above will have these names: + +* `AnotherInstantiationName/FooTest.DoesBlah/0` for `"cat"` +* `AnotherInstantiationName/FooTest.DoesBlah/1` for `"dog"` +* `AnotherInstantiationName/FooTest.HasBlahBlah/0` for `"cat"` +* `AnotherInstantiationName/FooTest.HasBlahBlah/1` for `"dog"` + +Please note that `INSTANTIATE_TEST_CASE_P` will instantiate *all* tests in the +given test case, whether their definitions come before or *after* the +`INSTANTIATE_TEST_CASE_P` statement. + +You can see sample7_unittest.cc and sample8_unittest.cc for more examples. + +**Availability**: Linux, Windows (requires MSVC 8.0 or above), Mac + +### Creating Value-Parameterized Abstract Tests + +In the above, we define and instantiate `FooTest` in the *same* source file. +Sometimes you may want to define value-parameterized tests in a library and let +other people instantiate them later. This pattern is known as *abstract tests*. +As an example of its application, when you are designing an interface you can +write a standard suite of abstract tests (perhaps using a factory function as +the test parameter) that all implementations of the interface are expected to +pass. When someone implements the interface, they can instantiate your suite to +get all the interface-conformance tests for free. + +To define abstract tests, you should organize your code like this: + +1. Put the definition of the parameterized test fixture class (e.g. `FooTest`) + in a header file, say `foo_param_test.h`. Think of this as *declaring* your + abstract tests. +1. Put the `TEST_P` definitions in `foo_param_test.cc`, which includes + `foo_param_test.h`. Think of this as *implementing* your abstract tests. + +Once they are defined, you can instantiate them by including `foo_param_test.h`, +invoking `INSTANTIATE_TEST_CASE_P()`, and depending on the library target that +contains `foo_param_test.cc`. You can instantiate the same abstract test case +multiple times, possibly in different source files. + +### Specifying Names for Value-Parameterized Test Parameters + +The optional last argument to `INSTANTIATE_TEST_CASE_P()` allows the user to +specify a function or functor that generates custom test name suffixes based on +the test parameters. The function should accept one argument of type +`testing::TestParamInfo<class ParamType>`, and return `std::string`. + +`testing::PrintToStringParamName` is a builtin test suffix generator that +returns the value of `testing::PrintToString(GetParam())`. It does not work for +`std::string` or C strings. + +NOTE: test names must be non-empty, unique, and may only contain ASCII +alphanumeric characters. In particular, they [should not contain +underscores](https://g3doc.corp.google.com/third_party/googletest/googletest/g3doc/faq.md#no-underscores). + +```c++ +class MyTestCase : public testing::TestWithParam<int> {}; + +TEST_P(MyTestCase, MyTest) +{ + std::cout << "Example Test Param: " << GetParam() << std::endl; +} + +INSTANTIATE_TEST_CASE_P(MyGroup, MyTestCase, testing::Range(0, 10), + testing::PrintToStringParamName()); +``` + +## Typed Tests</id> + +Suppose you have multiple implementations of the same interface and want to make +sure that all of them satisfy some common requirements. Or, you may have defined +several types that are supposed to conform to the same "concept" and you want to +verify it. In both cases, you want the same test logic repeated for different +types. + +While you can write one `TEST` or `TEST_F` for each type you want to test (and +you may even factor the test logic into a function template that you invoke from +the `TEST`), it's tedious and doesn't scale: if you want `m` tests over `n` +types, you'll end up writing `m*n` `TEST`s. + +*Typed tests* allow you to repeat the same test logic over a list of types. You +only need to write the test logic once, although you must know the type list +when writing typed tests. Here's how you do it: + +First, define a fixture class template. It should be parameterized by a type. +Remember to derive it from `::testing::Test`: + +```c++ +template <typename T> +class FooTest : public ::testing::Test { + public: + ... + typedef std::list<T> List; + static T shared_; + T value_; +}; +``` + +Next, associate a list of types with the test case, which will be repeated for +each type in the list: + +```c++ +using MyTypes = ::testing::Types<char, int, unsigned int>; +TYPED_TEST_CASE(FooTest, MyTypes); +``` + +The type alias (`using` or `typedef`) is necessary for the `TYPED_TEST_CASE` +macro to parse correctly. Otherwise the compiler will think that each comma in +the type list introduces a new macro argument. + +Then, use `TYPED_TEST()` instead of `TEST_F()` to define a typed test for this +test case. You can repeat this as many times as you want: + +```c++ +TYPED_TEST(FooTest, DoesBlah) { + // Inside a test, refer to the special name TypeParam to get the type + // parameter. Since we are inside a derived class template, C++ requires + // us to visit the members of FooTest via 'this'. + TypeParam n = this->value_; + + // To visit static members of the fixture, add the 'TestFixture::' + // prefix. + n += TestFixture::shared_; + + // To refer to typedefs in the fixture, add the 'typename TestFixture::' + // prefix. The 'typename' is required to satisfy the compiler. + typename TestFixture::List values; + + values.push_back(n); + ... +} + +TYPED_TEST(FooTest, HasPropertyA) { ... } +``` + +You can see sample6_unittest.cc + +**Availability**: Linux, Windows (requires MSVC 8.0 or above), Mac + +## Type-Parameterized Tests + +*Type-parameterized tests* are like typed tests, except that they don't require +you to know the list of types ahead of time. Instead, you can define the test +logic first and instantiate it with different type lists later. You can even +instantiate it more than once in the same program. + +If you are designing an interface or concept, you can define a suite of +type-parameterized tests to verify properties that any valid implementation of +the interface/concept should have. Then, the author of each implementation can +just instantiate the test suite with their type to verify that it conforms to +the requirements, without having to write similar tests repeatedly. Here's an +example: + +First, define a fixture class template, as we did with typed tests: + +```c++ +template <typename T> +class FooTest : public ::testing::Test { + ... +}; +``` + +Next, declare that you will define a type-parameterized test case: + +```c++ +TYPED_TEST_CASE_P(FooTest); +``` + +Then, use `TYPED_TEST_P()` to define a type-parameterized test. You can repeat +this as many times as you want: + +```c++ +TYPED_TEST_P(FooTest, DoesBlah) { + // Inside a test, refer to TypeParam to get the type parameter. + TypeParam n = 0; + ... +} + +TYPED_TEST_P(FooTest, HasPropertyA) { ... } +``` + +Now the tricky part: you need to register all test patterns using the +`REGISTER_TYPED_TEST_CASE_P` macro before you can instantiate them. The first +argument of the macro is the test case name; the rest are the names of the tests +in this test case: + +```c++ +REGISTER_TYPED_TEST_CASE_P(FooTest, + DoesBlah, HasPropertyA); +``` + +Finally, you are free to instantiate the pattern with the types you want. If you +put the above code in a header file, you can `#include` it in multiple C++ +source files and instantiate it multiple times. + +```c++ +typedef ::testing::Types<char, int, unsigned int> MyTypes; +INSTANTIATE_TYPED_TEST_CASE_P(My, FooTest, MyTypes); +``` + +To distinguish different instances of the pattern, the first argument to the +`INSTANTIATE_TYPED_TEST_CASE_P` macro is a prefix that will be added to the +actual test case name. Remember to pick unique prefixes for different instances. + +In the special case where the type list contains only one type, you can write +that type directly without `::testing::Types<...>`, like this: + +```c++ +INSTANTIATE_TYPED_TEST_CASE_P(My, FooTest, int); +``` + +You can see `sample6_unittest.cc` for a complete example. + +**Availability**: Linux, Windows (requires MSVC 8.0 or above), Mac + +## Testing Private Code + +If you change your software's internal implementation, your tests should not +break as long as the change is not observable by users. Therefore, **per the +black-box testing principle, most of the time you should test your code through +its public interfaces.** + +**If you still find yourself needing to test internal implementation code, +consider if there's a better design.** The desire to test internal +implementation is often a sign that the class is doing too much. Consider +extracting an implementation class, and testing it. Then use that implementation +class in the original class. + +If you absolutely have to test non-public interface code though, you can. There +are two cases to consider: + +* Static functions ( *not* the same as static member functions!) or unnamed + namespaces, and +* Private or protected class members + +To test them, we use the following special techniques: + +* Both static functions and definitions/declarations in an unnamed namespace + are only visible within the same translation unit. To test them, you can + `#include` the entire `.cc` file being tested in your `*_test.cc` file. + (#including `.cc` files is not a good way to reuse code - you should not do + this in production code!) + + However, a better approach is to move the private code into the + `foo::internal` namespace, where `foo` is the namespace your project + normally uses, and put the private declarations in a `*-internal.h` file. + Your production `.cc` files and your tests are allowed to include this + internal header, but your clients are not. This way, you can fully test your + internal implementation without leaking it to your clients. + +* Private class members are only accessible from within the class or by + friends. To access a class' private members, you can declare your test + fixture as a friend to the class and define accessors in your fixture. Tests + using the fixture can then access the private members of your production + class via the accessors in the fixture. Note that even though your fixture + is a friend to your production class, your tests are not automatically + friends to it, as they are technically defined in sub-classes of the + fixture. + + Another way to test private members is to refactor them into an + implementation class, which is then declared in a `*-internal.h` file. Your + clients aren't allowed to include this header but your tests can. Such is + called the + [Pimpl](https://www.gamedev.net/articles/programming/general-and-gameplay-programming/the-c-pimpl-r1794/) + (Private Implementation) idiom. + + Or, you can declare an individual test as a friend of your class by adding + this line in the class body: + + ```c++ + FRIEND_TEST(TestCaseName, TestName); + ``` + + For example, + + ```c++ + // foo.h + +#include "gtest/gtest_prod.h" + + class Foo { + ... + private: + FRIEND_TEST(FooTest, BarReturnsZeroOnNull); + + int Bar(void* x); + }; + + // foo_test.cc + ... + TEST(FooTest, BarReturnsZeroOnNull) { + Foo foo; + EXPECT_EQ(0, foo.Bar(NULL)); // Uses Foo's private member Bar(). + } + ``` + + Pay special attention when your class is defined in a namespace, as you + should define your test fixtures and tests in the same namespace if you want + them to be friends of your class. For example, if the code to be tested + looks like: + + ```c++ + namespace my_namespace { + + class Foo { + friend class FooTest; + FRIEND_TEST(FooTest, Bar); + FRIEND_TEST(FooTest, Baz); + ... definition of the class Foo ... + }; + + } // namespace my_namespace + ``` + + Your test code should be something like: + + ```c++ + namespace my_namespace { + + class FooTest : public ::testing::Test { + protected: + ... + }; + + TEST_F(FooTest, Bar) { ... } + TEST_F(FooTest, Baz) { ... } + + } // namespace my_namespace + ``` + + + ## "Catching" Failures + +If you are building a testing utility on top of googletest, you'll want to test +your utility. What framework would you use to test it? googletest, of course. + +The challenge is to verify that your testing utility reports failures correctly. +In frameworks that report a failure by throwing an exception, you could catch +the exception and assert on it. But googletest doesn't use exceptions, so how do +we test that a piece of code generates an expected failure? + +gunit-spi.h contains some constructs to do this. After #including this header, +you can use + +```c++ + EXPECT_FATAL_FAILURE(statement, substring); +``` + +to assert that `statement` generates a fatal (e.g. `ASSERT_*`) failure in the +current thread whose message contains the given `substring`, or use + +```c++ + EXPECT_NONFATAL_FAILURE(statement, substring); +``` + +if you are expecting a non-fatal (e.g. `EXPECT_*`) failure. + +Only failures in the current thread are checked to determine the result of this +type of expectations. If `statement` creates new threads, failures in these +threads are also ignored. If you want to catch failures in other threads as +well, use one of the following macros instead: + +```c++ + EXPECT_FATAL_FAILURE_ON_ALL_THREADS(statement, substring); + EXPECT_NONFATAL_FAILURE_ON_ALL_THREADS(statement, substring); +``` + +NOTE: Assertions from multiple threads are currently not supported on Windows. + +For technical reasons, there are some caveats: + +1. You cannot stream a failure message to either macro. + +1. `statement` in `EXPECT_FATAL_FAILURE{_ON_ALL_THREADS}()` cannot reference + local non-static variables or non-static members of `this` object. + +1. `statement` in `EXPECT_FATAL_FAILURE{_ON_ALL_THREADS}()()` cannot return a + value. + + +## Getting the Current Test's Name + +Sometimes a function may need to know the name of the currently running test. +For example, you may be using the `SetUp()` method of your test fixture to set +the golden file name based on which test is running. The `::testing::TestInfo` +class has this information: + +```c++ +namespace testing { + +class TestInfo { + public: + // Returns the test case name and the test name, respectively. + // + // Do NOT delete or free the return value - it's managed by the + // TestInfo class. + const char* test_case_name() const; + const char* name() const; +}; + +} +``` + +To obtain a `TestInfo` object for the currently running test, call +`current_test_info()` on the `UnitTest` singleton object: + +```c++ + // Gets information about the currently running test. + // Do NOT delete the returned object - it's managed by the UnitTest class. + const ::testing::TestInfo* const test_info = + ::testing::UnitTest::GetInstance()->current_test_info(); + + + + printf("We are in test %s of test case %s.\n", + test_info->name(), + test_info->test_case_name()); +``` + +`current_test_info()` returns a null pointer if no test is running. In +particular, you cannot find the test case name in `TestCaseSetUp()`, +`TestCaseTearDown()` (where you know the test case name implicitly), or +functions called from them. + +**Availability**: Linux, Windows, Mac. + +## Extending googletest by Handling Test Events + +googletest provides an **event listener API** to let you receive notifications +about the progress of a test program and test failures. The events you can +listen to include the start and end of the test program, a test case, or a test +method, among others. You may use this API to augment or replace the standard +console output, replace the XML output, or provide a completely different form +of output, such as a GUI or a database. You can also use test events as +checkpoints to implement a resource leak checker, for example. + +**Availability**: Linux, Windows, Mac. + +### Defining Event Listeners + +To define a event listener, you subclass either testing::TestEventListener or +testing::EmptyTestEventListener The former is an (abstract) interface, where +*each pure virtual method can be overridden to handle a test event* (For +example, when a test starts, the `OnTestStart()` method will be called.). The +latter provides an empty implementation of all methods in the interface, such +that a subclass only needs to override the methods it cares about. + +When an event is fired, its context is passed to the handler function as an +argument. The following argument types are used: + +* UnitTest reflects the state of the entire test program, +* TestCase has information about a test case, which can contain one or more + tests, +* TestInfo contains the state of a test, and +* TestPartResult represents the result of a test assertion. + +An event handler function can examine the argument it receives to find out +interesting information about the event and the test program's state. + +Here's an example: + +```c++ + class MinimalistPrinter : public ::testing::EmptyTestEventListener { + // Called before a test starts. + virtual void OnTestStart(const ::testing::TestInfo& test_info) { + printf("*** Test %s.%s starting.\n", + test_info.test_case_name(), test_info.name()); + } + + // Called after a failed assertion or a SUCCESS(). + virtual void OnTestPartResult(const ::testing::TestPartResult& test_part_result) { + printf("%s in %s:%d\n%s\n", + test_part_result.failed() ? "*** Failure" : "Success", + test_part_result.file_name(), + test_part_result.line_number(), + test_part_result.summary()); + } + + // Called after a test ends. + virtual void OnTestEnd(const ::testing::TestInfo& test_info) { + printf("*** Test %s.%s ending.\n", + test_info.test_case_name(), test_info.name()); + } + }; +``` + +### Using Event Listeners + +To use the event listener you have defined, add an instance of it to the +googletest event listener list (represented by class TestEventListeners - note +the "s" at the end of the name) in your `main()` function, before calling +`RUN_ALL_TESTS()`: + +```c++ +int main(int argc, char** argv) { + ::testing::InitGoogleTest(&argc, argv); + // Gets hold of the event listener list. + ::testing::TestEventListeners& listeners = + ::testing::UnitTest::GetInstance()->listeners(); + // Adds a listener to the end. googletest takes the ownership. + listeners.Append(new MinimalistPrinter); + return RUN_ALL_TESTS(); +} +``` + +There's only one problem: the default test result printer is still in effect, so +its output will mingle with the output from your minimalist printer. To suppress +the default printer, just release it from the event listener list and delete it. +You can do so by adding one line: + +```c++ + ... + delete listeners.Release(listeners.default_result_printer()); + listeners.Append(new MinimalistPrinter); + return RUN_ALL_TESTS(); +``` + +Now, sit back and enjoy a completely different output from your tests. For more +details, you can read this sample9_unittest.cc + +You may append more than one listener to the list. When an `On*Start()` or +`OnTestPartResult()` event is fired, the listeners will receive it in the order +they appear in the list (since new listeners are added to the end of the list, +the default text printer and the default XML generator will receive the event +first). An `On*End()` event will be received by the listeners in the *reverse* +order. This allows output by listeners added later to be framed by output from +listeners added earlier. + +### Generating Failures in Listeners + +You may use failure-raising macros (`EXPECT_*()`, `ASSERT_*()`, `FAIL()`, etc) +when processing an event. There are some restrictions: + +1. You cannot generate any failure in `OnTestPartResult()` (otherwise it will + cause `OnTestPartResult()` to be called recursively). +1. A listener that handles `OnTestPartResult()` is not allowed to generate any + failure. + +When you add listeners to the listener list, you should put listeners that +handle `OnTestPartResult()` *before* listeners that can generate failures. This +ensures that failures generated by the latter are attributed to the right test +by the former. + +We have a sample of failure-raising listener sample10_unittest.cc + +## Running Test Programs: Advanced Options + +googletest test programs are ordinary executables. Once built, you can run them +directly and affect their behavior via the following environment variables +and/or command line flags. For the flags to work, your programs must call +`::testing::InitGoogleTest()` before calling `RUN_ALL_TESTS()`. + +To see a list of supported flags and their usage, please run your test program +with the `--help` flag. You can also use `-h`, `-?`, or `/?` for short. + +If an option is specified both by an environment variable and by a flag, the +latter takes precedence. + +### Selecting Tests + +#### Listing Test Names + +Sometimes it is necessary to list the available tests in a program before +running them so that a filter may be applied if needed. Including the flag +`--gtest_list_tests` overrides all other flags and lists tests in the following +format: + +```none +TestCase1. + TestName1 + TestName2 +TestCase2. + TestName +``` + +None of the tests listed are actually run if the flag is provided. There is no +corresponding environment variable for this flag. + +**Availability**: Linux, Windows, Mac. + +#### Running a Subset of the Tests + +By default, a googletest program runs all tests the user has defined. Sometimes, +you want to run only a subset of the tests (e.g. for debugging or quickly +verifying a change). If you set the `GTEST_FILTER` environment variable or the +`--gtest_filter` flag to a filter string, googletest will only run the tests +whose full names (in the form of `TestCaseName.TestName`) match the filter. + +The format of a filter is a '`:`'-separated list of wildcard patterns (called +the *positive patterns*) optionally followed by a '`-`' and another +'`:`'-separated pattern list (called the *negative patterns*). A test matches +the filter if and only if it matches any of the positive patterns but does not +match any of the negative patterns. + +A pattern may contain `'*'` (matches any string) or `'?'` (matches any single +character). For convenience, the filter + +`'*-NegativePatterns'` can be also written as `'-NegativePatterns'`. + +For example: + +* `./foo_test` Has no flag, and thus runs all its tests. +* `./foo_test --gtest_filter=*` Also runs everything, due to the single + match-everything `*` value. +* `./foo_test --gtest_filter=FooTest.*` Runs everything in test case `FooTest` + . +* `./foo_test --gtest_filter=*Null*:*Constructor*` Runs any test whose full + name contains either `"Null"` or `"Constructor"` . +* `./foo_test --gtest_filter=-*DeathTest.*` Runs all non-death tests. +* `./foo_test --gtest_filter=FooTest.*-FooTest.Bar` Runs everything in test + case `FooTest` except `FooTest.Bar`. +* `./foo_test --gtest_filter=FooTest.*:BarTest.*-FooTest.Bar:BarTest.Foo` Runs + everything in test case `FooTest` except `FooTest.Bar` and everything in + test case `BarTest` except `BarTest.Foo`. + +#### Temporarily Disabling Tests + +If you have a broken test that you cannot fix right away, you can add the +`DISABLED_` prefix to its name. This will exclude it from execution. This is +better than commenting out the code or using `#if 0`, as disabled tests are +still compiled (and thus won't rot). + +If you need to disable all tests in a test case, you can either add `DISABLED_` +to the front of the name of each test, or alternatively add it to the front of +the test case name. + +For example, the following tests won't be run by googletest, even though they +will still be compiled: + +```c++ +// Tests that Foo does Abc. +TEST(FooTest, DISABLED_DoesAbc) { ... } + +class DISABLED_BarTest : public ::testing::Test { ... }; + +// Tests that Bar does Xyz. +TEST_F(DISABLED_BarTest, DoesXyz) { ... } +``` + +NOTE: This feature should only be used for temporary pain-relief. You still have +to fix the disabled tests at a later date. As a reminder, googletest will print +a banner warning you if a test program contains any disabled tests. + +TIP: You can easily count the number of disabled tests you have using `gsearch` +and/or `grep`. This number can be used as a metric for improving your test +quality. + +**Availability**: Linux, Windows, Mac. + +#### Temporarily Enabling Disabled Tests + +To include disabled tests in test execution, just invoke the test program with +the `--gtest_also_run_disabled_tests` flag or set the +`GTEST_ALSO_RUN_DISABLED_TESTS` environment variable to a value other than `0`. +You can combine this with the `--gtest_filter` flag to further select which +disabled tests to run. + +**Availability**: Linux, Windows, Mac. + +### Repeating the Tests + +Once in a while you'll run into a test whose result is hit-or-miss. Perhaps it +will fail only 1% of the time, making it rather hard to reproduce the bug under +a debugger. This can be a major source of frustration. + +The `--gtest_repeat` flag allows you to repeat all (or selected) test methods in +a program many times. Hopefully, a flaky test will eventually fail and give you +a chance to debug. Here's how to use it: + +```none +$ foo_test --gtest_repeat=1000 +Repeat foo_test 1000 times and don't stop at failures. + +$ foo_test --gtest_repeat=-1 +A negative count means repeating forever. + +$ foo_test --gtest_repeat=1000 --gtest_break_on_failure +Repeat foo_test 1000 times, stopping at the first failure. This +is especially useful when running under a debugger: when the test +fails, it will drop into the debugger and you can then inspect +variables and stacks. + +$ foo_test --gtest_repeat=1000 --gtest_filter=FooBar.* +Repeat the tests whose name matches the filter 1000 times. +``` + +If your test program contains [global set-up/tear-down](#GlobalSetUp) code, it +will be repeated in each iteration as well, as the flakiness may be in it. You +can also specify the repeat count by setting the `GTEST_REPEAT` environment +variable. + +**Availability**: Linux, Windows, Mac. + +### Shuffling the Tests + +You can specify the `--gtest_shuffle` flag (or set the `GTEST_SHUFFLE` +environment variable to `1`) to run the tests in a program in a random order. +This helps to reveal bad dependencies between tests. + +By default, googletest uses a random seed calculated from the current time. +Therefore you'll get a different order every time. The console output includes +the random seed value, such that you can reproduce an order-related test failure +later. To specify the random seed explicitly, use the `--gtest_random_seed=SEED` +flag (or set the `GTEST_RANDOM_SEED` environment variable), where `SEED` is an +integer in the range [0, 99999]. The seed value 0 is special: it tells +googletest to do the default behavior of calculating the seed from the current +time. + +If you combine this with `--gtest_repeat=N`, googletest will pick a different +random seed and re-shuffle the tests in each iteration. + +**Availability**: Linux, Windows, Mac. + +### Controlling Test Output + +#### Colored Terminal Output + +googletest can use colors in its terminal output to make it easier to spot the +important information: + +... +<span style="color:green">[----------]<span style="color:black"> 1 test from FooTest +<span style="color:green">[ RUN ]<span style="color:black"> FooTest.DoesAbc +<span style="color:green">[ OK ]<span style="color:black"> FooTest.DoesAbc +<span style="color:green">[----------]<span style="color:black"> 2 tests from BarTest +<span style="color:green">[ RUN ]<span style="color:black"> BarTest.HasXyzProperty +<span style="color:green">[ OK ]<span style="color:black"> BarTest.HasXyzProperty +<span style="color:green">[ RUN ]<span style="color:black"> BarTest.ReturnsTrueOnSuccess +... some error messages ... +<span style="color:red">[ FAILED ] <span style="color:black">BarTest.ReturnsTrueOnSuccess +... +<span style="color:green">[==========]<span style="color:black"> 30 tests from 14 test cases ran. +<span style="color:green">[ PASSED ]<span style="color:black"> 28 tests. +<span style="color:red">[ FAILED ]<span style="color:black"> 2 tests, listed below: +<span style="color:red">[ FAILED ]<span style="color:black"> BarTest.ReturnsTrueOnSuccess +<span style="color:red">[ FAILED ]<span style="color:black"> AnotherTest.DoesXyz + + 2 FAILED TESTS + +You can set the `GTEST_COLOR` environment variable or the `--gtest_color` +command line flag to `yes`, `no`, or `auto` (the default) to enable colors, +disable colors, or let googletest decide. When the value is `auto`, googletest +will use colors if and only if the output goes to a terminal and (on non-Windows +platforms) the `TERM` environment variable is set to `xterm` or `xterm-color`. + +> +> **Availability**: Linux, Windows, Mac. + +#### Suppressing the Elapsed Time + +By default, googletest prints the time it takes to run each test. To disable +that, run the test program with the `--gtest_print_time=0` command line flag, or +set the GTEST_PRINT_TIME environment variable to `0`. + +**Availability**: Linux, Windows, Mac. + +#### Suppressing UTF-8 Text Output + +In case of assertion failures, googletest prints expected and actual values of +type `string` both as hex-encoded strings as well as in readable UTF-8 text if +they contain valid non-ASCII UTF-8 characters. If you want to suppress the UTF-8 +text because, for example, you don't have an UTF-8 compatible output medium, run +the test program with `--gtest_print_utf8=0` or set the `GTEST_PRINT_UTF8` +environment variable to `0`. + +**Availability**: Linux, Windows, Mac. + + +#### Generating an XML Report + +googletest can emit a detailed XML report to a file in addition to its normal +textual output. The report contains the duration of each test, and thus can help +you identify slow tests. The report is also used by the http://unittest +dashboard to show per-test-method error messages. + +To generate the XML report, set the `GTEST_OUTPUT` environment variable or the +`--gtest_output` flag to the string `"xml:path_to_output_file"`, which will +create the file at the given location. You can also just use the string `"xml"`, +in which case the output can be found in the `test_detail.xml` file in the +current directory. + +If you specify a directory (for example, `"xml:output/directory/"` on Linux or +`"xml:output\directory\"` on Windows), googletest will create the XML file in +that directory, named after the test executable (e.g. `foo_test.xml` for test +program `foo_test` or `foo_test.exe`). If the file already exists (perhaps left +over from a previous run), googletest will pick a different name (e.g. +`foo_test_1.xml`) to avoid overwriting it. + + +The report is based on the `junitreport` Ant task. Since that format was +originally intended for Java, a little interpretation is required to make it +apply to googletest tests, as shown here: + +```xml +<testsuites name="AllTests" ...> + <testsuite name="test_case_name" ...> + <testcase name="test_name" ...> + <failure message="..."/> + <failure message="..."/> + <failure message="..."/> + </testcase> + </testsuite> +</testsuites> +``` + +* The root `<testsuites>` element corresponds to the entire test program. +* `<testsuite>` elements correspond to googletest test cases. +* `<testcase>` elements correspond to googletest test functions. + +For instance, the following program + +```c++ +TEST(MathTest, Addition) { ... } +TEST(MathTest, Subtraction) { ... } +TEST(LogicTest, NonContradiction) { ... } +``` + +could generate this report: + +```xml +<?xml version="1.0" encoding="UTF-8"?> +<testsuites tests="3" failures="1" errors="0" time="0.035" timestamp="2011-10-31T18:52:42" name="AllTests"> + <testsuite name="MathTest" tests="2" failures="1" errors="0" time="0.015"> + <testcase name="Addition" status="run" time="0.007" classname=""> + <failure message="Value of: add(1, 1)
 Actual: 3
Expected: 2" type="">...</failure> + <failure message="Value of: add(1, -1)
 Actual: 1
Expected: 0" type="">...</failure> + </testcase> + <testcase name="Subtraction" status="run" time="0.005" classname=""> + </testcase> + </testsuite> + <testsuite name="LogicTest" tests="1" failures="0" errors="0" time="0.005"> + <testcase name="NonContradiction" status="run" time="0.005" classname=""> + </testcase> + </testsuite> +</testsuites> +``` + +Things to note: + +* The `tests` attribute of a `<testsuites>` or `<testsuite>` element tells how + many test functions the googletest program or test case contains, while the + `failures` attribute tells how many of them failed. + +* The `time` attribute expresses the duration of the test, test case, or + entire test program in seconds. + +* The `timestamp` attribute records the local date and time of the test + execution. + +* Each `<failure>` element corresponds to a single failed googletest + assertion. + +**Availability**: Linux, Windows, Mac. + +#### Generating an JSON Report + +googletest can also emit a JSON report as an alternative format to XML. To +generate the JSON report, set the `GTEST_OUTPUT` environment variable or the +`--gtest_output` flag to the string `"json:path_to_output_file"`, which will +create the file at the given location. You can also just use the string +`"json"`, in which case the output can be found in the `test_detail.json` file +in the current directory. + +The report format conforms to the following JSON Schema: + +```json +{ + "$schema": "http://json-schema.org/schema#", + "type": "object", + "definitions": { + "TestCase": { + "type": "object", + "properties": { + "name": { "type": "string" }, + "tests": { "type": "integer" }, + "failures": { "type": "integer" }, + "disabled": { "type": "integer" }, + "time": { "type": "string" }, + "testsuite": { + "type": "array", + "items": { + "$ref": "#/definitions/TestInfo" + } + } + } + }, + "TestInfo": { + "type": "object", + "properties": { + "name": { "type": "string" }, + "status": { + "type": "string", + "enum": ["RUN", "NOTRUN"] + }, + "time": { "type": "string" }, + "classname": { "type": "string" }, + "failures": { + "type": "array", + "items": { + "$ref": "#/definitions/Failure" + } + } + } + }, + "Failure": { + "type": "object", + "properties": { + "failures": { "type": "string" }, + "type": { "type": "string" } + } + } + }, + "properties": { + "tests": { "type": "integer" }, + "failures": { "type": "integer" }, + "disabled": { "type": "integer" }, + "errors": { "type": "integer" }, + "timestamp": { + "type": "string", + "format": "date-time" + }, + "time": { "type": "string" }, + "name": { "type": "string" }, + "testsuites": { + "type": "array", + "items": { + "$ref": "#/definitions/TestCase" + } + } + } +} +``` + +The report uses the format that conforms to the following Proto3 using the [JSON +encoding](https://developers.google.com/protocol-buffers/docs/proto3#json): + +```proto +syntax = "proto3"; + +package googletest; + +import "google/protobuf/timestamp.proto"; +import "google/protobuf/duration.proto"; + +message UnitTest { + int32 tests = 1; + int32 failures = 2; + int32 disabled = 3; + int32 errors = 4; + google.protobuf.Timestamp timestamp = 5; + google.protobuf.Duration time = 6; + string name = 7; + repeated TestCase testsuites = 8; +} + +message TestCase { + string name = 1; + int32 tests = 2; + int32 failures = 3; + int32 disabled = 4; + int32 errors = 5; + google.protobuf.Duration time = 6; + repeated TestInfo testsuite = 7; +} + +message TestInfo { + string name = 1; + enum Status { + RUN = 0; + NOTRUN = 1; + } + Status status = 2; + google.protobuf.Duration time = 3; + string classname = 4; + message Failure { + string failures = 1; + string type = 2; + } + repeated Failure failures = 5; +} +``` + +For instance, the following program + +```c++ +TEST(MathTest, Addition) { ... } +TEST(MathTest, Subtraction) { ... } +TEST(LogicTest, NonContradiction) { ... } +``` + +could generate this report: + +```json +{ + "tests": 3, + "failures": 1, + "errors": 0, + "time": "0.035s", + "timestamp": "2011-10-31T18:52:42Z" + "name": "AllTests", + "testsuites": [ + { + "name": "MathTest", + "tests": 2, + "failures": 1, + "errors": 0, + "time": "0.015s", + "testsuite": [ + { + "name": "Addition", + "status": "RUN", + "time": "0.007s", + "classname": "", + "failures": [ + { + "message": "Value of: add(1, 1)\x0A Actual: 3\x0AExpected: 2", + "type": "" + }, + { + "message": "Value of: add(1, -1)\x0A Actual: 1\x0AExpected: 0", + "type": "" + } + ] + }, + { + "name": "Subtraction", + "status": "RUN", + "time": "0.005s", + "classname": "" + } + ] + } + { + "name": "LogicTest", + "tests": 1, + "failures": 0, + "errors": 0, + "time": "0.005s", + "testsuite": [ + { + "name": "NonContradiction", + "status": "RUN", + "time": "0.005s", + "classname": "" + } + ] + } + ] +} +``` + +IMPORTANT: The exact format of the JSON document is subject to change. + +**Availability**: Linux, Windows, Mac. + +### Controlling How Failures Are Reported + +#### Turning Assertion Failures into Break-Points + +When running test programs under a debugger, it's very convenient if the +debugger can catch an assertion failure and automatically drop into interactive +mode. googletest's *break-on-failure* mode supports this behavior. + +To enable it, set the `GTEST_BREAK_ON_FAILURE` environment variable to a value +other than `0` . Alternatively, you can use the `--gtest_break_on_failure` +command line flag. + +**Availability**: Linux, Windows, Mac. + +#### Disabling Catching Test-Thrown Exceptions + +googletest can be used either with or without exceptions enabled. If a test +throws a C++ exception or (on Windows) a structured exception (SEH), by default +googletest catches it, reports it as a test failure, and continues with the next +test method. This maximizes the coverage of a test run. Also, on Windows an +uncaught exception will cause a pop-up window, so catching the exceptions allows +you to run the tests automatically. + +When debugging the test failures, however, you may instead want the exceptions +to be handled by the debugger, such that you can examine the call stack when an +exception is thrown. To achieve that, set the `GTEST_CATCH_EXCEPTIONS` +environment variable to `0`, or use the `--gtest_catch_exceptions=0` flag when +running the tests. + +**Availability**: Linux, Windows, Mac. + |