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diff --git a/googletest/docs/faq.md b/googletest/docs/faq.md index 1e2c341..7d42ff7 100644 --- a/googletest/docs/faq.md +++ b/googletest/docs/faq.md @@ -1,337 +1,203 @@ +# Googletest FAQ -If you cannot find the answer to your question here, and you have read -[Primer](primer.md) and [AdvancedGuide](advanced.md), send it to -googletestframework@googlegroups.com. +## Why should test case names and test names not contain underscore? -## Why should I use Google Test instead of my favorite C++ testing framework? ## +Underscore (`_`) is special, as C++ reserves the following to be used by the +compiler and the standard library: -First, let us say clearly that we don't want to get into the debate of -which C++ testing framework is **the best**. There exist many fine -frameworks for writing C++ tests, and we have tremendous respect for -the developers and users of them. We don't think there is (or will -be) a single best framework - you have to pick the right tool for the -particular task you are tackling. +1. any identifier that starts with an `_` followed by an upper-case letter, and +1. any identifier that contains two consecutive underscores (i.e. `__`) + *anywhere* in its name. -We created Google Test because we couldn't find the right combination -of features and conveniences in an existing framework to satisfy _our_ -needs. The following is a list of things that _we_ like about Google -Test. We don't claim them to be unique to Google Test - rather, the -combination of them makes Google Test the choice for us. We hope this -list can help you decide whether it is for you too. - - * Google Test is designed to be portable: it doesn't require exceptions or RTTI; it works around various bugs in various compilers and environments; etc. As a result, it works on Linux, Mac OS X, Windows and several embedded operating systems. - * Nonfatal assertions (`EXPECT_*`) have proven to be great time savers, as they allow a test to report multiple failures in a single edit-compile-test cycle. - * It's easy to write assertions that generate informative messages: you just use the stream syntax to append any additional information, e.g. `ASSERT_EQ(5, Foo(i)) << " where i = " << i;`. It doesn't require a new set of macros or special functions. - * Google Test automatically detects your tests and doesn't require you to enumerate them in order to run them. - * Death tests are pretty handy for ensuring that your asserts in production code are triggered by the right conditions. - * `SCOPED_TRACE` helps you understand the context of an assertion failure when it comes from inside a sub-routine or loop. - * You can decide which tests to run using name patterns. This saves time when you want to quickly reproduce a test failure. - * Google Test can generate XML test result reports that can be parsed by popular continuous build system like Hudson. - * Simple things are easy in Google Test, while hard things are possible: in addition to advanced features like [global test environments](advanced.md#global-set-up-and-tear-down) and tests parameterized by [values](advanced.md#value-parameterized-tests) or [types](docs/advanced.md#typed-tests), Google Test supports various ways for the user to extend the framework -- if Google Test doesn't do something out of the box, chances are that a user can implement the feature using Google Test's public API, without changing Google Test itself. In particular, you can: - * expand your testing vocabulary by defining [custom predicates](advanced.md#predicate-assertions-for-better-error-messages), - * teach Google Test how to [print your types](advanced.md#teaching-google-test-how-to-print-your-values), - * define your own testing macros or utilities and verify them using Google Test's [Service Provider Interface](advanced.md#catching-failures), and - * reflect on the test cases or change the test output format by intercepting the [test events](advanced.md#extending-google-test-by-handling-test-events). - -## I'm getting warnings when compiling Google Test. Would you fix them? ## - -We strive to minimize compiler warnings Google Test generates. Before releasing a new version, we test to make sure that it doesn't generate warnings when compiled using its CMake script on Windows, Linux, and Mac OS. - -Unfortunately, this doesn't mean you are guaranteed to see no warnings when compiling Google Test in your environment: - - * You may be using a different compiler as we use, or a different version of the same compiler. We cannot possibly test for all compilers. - * You may be compiling on a different platform as we do. - * Your project may be using different compiler flags as we do. - -It is not always possible to make Google Test warning-free for everyone. Or, it may not be desirable if the warning is rarely enabled and fixing the violations makes the code more complex. - -If you see warnings when compiling Google Test, we suggest that you use the `-isystem` flag (assuming your are using GCC) to mark Google Test headers as system headers. That'll suppress warnings from Google Test headers. - -## Why should not test case names and test names contain underscore? ## - -Underscore (`_`) is special, as C++ reserves the following to be used by -the compiler and the standard library: - - 1. any identifier that starts with an `_` followed by an upper-case letter, and - 1. any identifier that contains two consecutive underscores (i.e. `__`) _anywhere_ in its name. - -User code is _prohibited_ from using such identifiers. +User code is *prohibited* from using such identifiers. Now let's look at what this means for `TEST` and `TEST_F`. Currently `TEST(TestCaseName, TestName)` generates a class named -`TestCaseName_TestName_Test`. What happens if `TestCaseName` or `TestName` +`TestCaseName_TestName_Test`. What happens if `TestCaseName` or `TestName` contains `_`? - 1. If `TestCaseName` starts with an `_` followed by an upper-case letter (say, `_Foo`), we end up with `_Foo_TestName_Test`, which is reserved and thus invalid. - 1. If `TestCaseName` ends with an `_` (say, `Foo_`), we get `Foo__TestName_Test`, which is invalid. - 1. If `TestName` starts with an `_` (say, `_Bar`), we get `TestCaseName__Bar_Test`, which is invalid. - 1. If `TestName` ends with an `_` (say, `Bar_`), we get `TestCaseName_Bar__Test`, which is invalid. +1. If `TestCaseName` starts with an `_` followed by an upper-case letter (say, + `_Foo`), we end up with `_Foo_TestName_Test`, which is reserved and thus + invalid. +1. If `TestCaseName` ends with an `_` (say, `Foo_`), we get + `Foo__TestName_Test`, which is invalid. +1. If `TestName` starts with an `_` (say, `_Bar`), we get + `TestCaseName__Bar_Test`, which is invalid. +1. If `TestName` ends with an `_` (say, `Bar_`), we get + `TestCaseName_Bar__Test`, which is invalid. + +So clearly `TestCaseName` and `TestName` cannot start or end with `_` (Actually, +`TestCaseName` can start with `_` -- as long as the `_` isn't followed by an +upper-case letter. But that's getting complicated. So for simplicity we just say +that it cannot start with `_`.). -So clearly `TestCaseName` and `TestName` cannot start or end with `_` -(Actually, `TestCaseName` can start with `_` -- as long as the `_` isn't -followed by an upper-case letter. But that's getting complicated. So -for simplicity we just say that it cannot start with `_`.). +It may seem fine for `TestCaseName` and `TestName` to contain `_` in the middle. +However, consider this: -It may seem fine for `TestCaseName` and `TestName` to contain `_` in the -middle. However, consider this: ```c++ TEST(Time, Flies_Like_An_Arrow) { ... } TEST(Time_Flies, Like_An_Arrow) { ... } ``` Now, the two `TEST`s will both generate the same class -(`Time_Files_Like_An_Arrow_Test`). That's not good. - -So for simplicity, we just ask the users to avoid `_` in `TestCaseName` -and `TestName`. The rule is more constraining than necessary, but it's -simple and easy to remember. It also gives Google Test some wiggle -room in case its implementation needs to change in the future. - -If you violate the rule, there may not be immediately consequences, -but your test may (just may) break with a new compiler (or a new -version of the compiler you are using) or with a new version of Google -Test. Therefore it's best to follow the rule. - -## Why is it not recommended to install a pre-compiled copy of Google Test (for example, into /usr/local)? ## - -In the early days, we said that you could install -compiled Google Test libraries on `*`nix systems using `make install`. -Then every user of your machine can write tests without -recompiling Google Test. - -This seemed like a good idea, but it has a -got-cha: every user needs to compile their tests using the _same_ compiler -flags used to compile the installed Google Test libraries; otherwise -they may run into undefined behaviors (i.e. the tests can behave -strangely and may even crash for no obvious reasons). - -Why? Because C++ has this thing called the One-Definition Rule: if -two C++ source files contain different definitions of the same -class/function/variable, and you link them together, you violate the -rule. The linker may or may not catch the error (in many cases it's -not required by the C++ standard to catch the violation). If it -doesn't, you get strange run-time behaviors that are unexpected and -hard to debug. - -If you compile Google Test and your test code using different compiler -flags, they may see different definitions of the same -class/function/variable (e.g. due to the use of `#if` in Google Test). -Therefore, for your sanity, we recommend to avoid installing pre-compiled -Google Test libraries. Instead, each project should compile -Google Test itself such that it can be sure that the same flags are -used for both Google Test and the tests. - -## How do I generate 64-bit binaries on Windows (using Visual Studio 2008)? ## - -(Answered by Trevor Robinson) - -Load the supplied Visual Studio solution file, either `msvc\gtest-md.sln` or -`msvc\gtest.sln`. Go through the migration wizard to migrate the -solution and project files to Visual Studio 2008. Select -`Configuration Manager...` from the `Build` menu. Select `<New...>` from -the `Active solution platform` dropdown. Select `x64` from the new -platform dropdown, leave `Copy settings from` set to `Win32` and -`Create new project platforms` checked, then click `OK`. You now have -`Win32` and `x64` platform configurations, selectable from the -`Standard` toolbar, which allow you to toggle between building 32-bit or -64-bit binaries (or both at once using Batch Build). - -In order to prevent build output files from overwriting one another, -you'll need to change the `Intermediate Directory` settings for the -newly created platform configuration across all the projects. To do -this, multi-select (e.g. using shift-click) all projects (but not the -solution) in the `Solution Explorer`. Right-click one of them and -select `Properties`. In the left pane, select `Configuration Properties`, -and from the `Configuration` dropdown, select `All Configurations`. -Make sure the selected platform is `x64`. For the -`Intermediate Directory` setting, change the value from -`$(PlatformName)\$(ConfigurationName)` to -`$(OutDir)\$(ProjectName)`. Click `OK` and then build the -solution. When the build is complete, the 64-bit binaries will be in -the `msvc\x64\Debug` directory. - -## Can I use Google Test on MinGW? ## - -We haven't tested this ourselves, but Per Abrahamsen reported that he -was able to compile and install Google Test successfully when using -MinGW from Cygwin. You'll need to configure it with: - -`PATH/TO/configure CC="gcc -mno-cygwin" CXX="g++ -mno-cygwin"` - -You should be able to replace the `-mno-cygwin` option with direct links -to the real MinGW binaries, but we haven't tried that. - -Caveats: - - * There are many warnings when compiling. - * `make check` will produce some errors as not all tests for Google Test itself are compatible with MinGW. - -We also have reports on successful cross compilation of Google Test -MinGW binaries on Linux using -[these instructions](http://wiki.wxwidgets.org/Cross-Compiling_Under_Linux#Cross-compiling_under_Linux_for_MS_Windows) -on the WxWidgets site. - -Please contact `googletestframework@googlegroups.com` if you are -interested in improving the support for MinGW. - -## Why does Google Test support EXPECT\_EQ(NULL, ptr) and ASSERT\_EQ(NULL, ptr) but not EXPECT\_NE(NULL, ptr) and ASSERT\_NE(NULL, ptr)? ## - -Due to some peculiarity of C++, it requires some non-trivial template -meta programming tricks to support using `NULL` as an argument of the -`EXPECT_XX()` and `ASSERT_XX()` macros. Therefore we only do it where -it's most needed (otherwise we make the implementation of Google Test -harder to maintain and more error-prone than necessary). - -The `EXPECT_EQ()` macro takes the _expected_ value as its first -argument and the _actual_ value as the second. It's reasonable that -someone wants to write `EXPECT_EQ(NULL, some_expression)`, and this -indeed was requested several times. Therefore we implemented it. - -The need for `EXPECT_NE(NULL, ptr)` isn't nearly as strong. When the -assertion fails, you already know that `ptr` must be `NULL`, so it -doesn't add any information to print ptr in this case. That means -`EXPECT_TRUE(ptr != NULL)` works just as well. - -If we were to support `EXPECT_NE(NULL, ptr)`, for consistency we'll -have to support `EXPECT_NE(ptr, NULL)` as well, as unlike `EXPECT_EQ`, -we don't have a convention on the order of the two arguments for -`EXPECT_NE`. This means using the template meta programming tricks -twice in the implementation, making it even harder to understand and -maintain. We believe the benefit doesn't justify the cost. - -Finally, with the growth of Google Mock's [matcher](../../googlemock/docs/CookBook.md#using-matchers-in-google-test-assertions) library, we are -encouraging people to use the unified `EXPECT_THAT(value, matcher)` -syntax more often in tests. One significant advantage of the matcher -approach is that matchers can be easily combined to form new matchers, -while the `EXPECT_NE`, etc, macros cannot be easily -combined. Therefore we want to invest more in the matchers than in the +(`Time_Flies_Like_An_Arrow_Test`). That's not good. + +So for simplicity, we just ask the users to avoid `_` in `TestCaseName` and +`TestName`. The rule is more constraining than necessary, but it's simple and +easy to remember. It also gives googletest some wiggle room in case its +implementation needs to change in the future. + +If you violate the rule, there may not be immediate consequences, but your test +may (just may) break with a new compiler (or a new version of the compiler you +are using) or with a new version of googletest. Therefore it's best to follow +the rule. + +## Why does googletest support `EXPECT_EQ(NULL, ptr)` and `ASSERT_EQ(NULL, ptr)` but not `EXPECT_NE(NULL, ptr)` and `ASSERT_NE(NULL, ptr)`? + +First of all you can use `EXPECT_NE(nullptr, ptr)` and `ASSERT_NE(nullptr, +ptr)`. This is the preferred syntax in the style guide because nullptr does not +have the type problems that NULL does. Which is why NULL does not work. + +Due to some peculiarity of C++, it requires some non-trivial template meta +programming tricks to support using `NULL` as an argument of the `EXPECT_XX()` +and `ASSERT_XX()` macros. Therefore we only do it where it's most needed +(otherwise we make the implementation of googletest harder to maintain and more +error-prone than necessary). + +The `EXPECT_EQ()` macro takes the *expected* value as its first argument and the +*actual* value as the second. It's reasonable that someone wants to write +`EXPECT_EQ(NULL, some_expression)`, and this indeed was requested several times. +Therefore we implemented it. + +The need for `EXPECT_NE(NULL, ptr)` isn't nearly as strong. When the assertion +fails, you already know that `ptr` must be `NULL`, so it doesn't add any +information to print `ptr` in this case. That means `EXPECT_TRUE(ptr != NULL)` +works just as well. + +If we were to support `EXPECT_NE(NULL, ptr)`, for consistency we'll have to +support `EXPECT_NE(ptr, NULL)` as well, as unlike `EXPECT_EQ`, we don't have a +convention on the order of the two arguments for `EXPECT_NE`. This means using +the template meta programming tricks twice in the implementation, making it even +harder to understand and maintain. We believe the benefit doesn't justify the +cost. + +Finally, with the growth of the gMock matcher library, we are encouraging people +to use the unified `EXPECT_THAT(value, matcher)` syntax more often in tests. One +significant advantage of the matcher approach is that matchers can be easily +combined to form new matchers, while the `EXPECT_NE`, etc, macros cannot be +easily combined. Therefore we want to invest more in the matchers than in the `EXPECT_XX()` macros. -## Does Google Test support running tests in parallel? ## - -Test runners tend to be tightly coupled with the build/test -environment, and Google Test doesn't try to solve the problem of -running tests in parallel. Instead, we tried to make Google Test work -nicely with test runners. For example, Google Test's XML report -contains the time spent on each test, and its `gtest_list_tests` and -`gtest_filter` flags can be used for splitting the execution of test -methods into multiple processes. These functionalities can help the -test runner run the tests in parallel. +## I need to test that different implementations of an interface satisfy some common requirements. Should I use typed tests or value-parameterized tests? -## Why don't Google Test run the tests in different threads to speed things up? ## +For testing various implementations of the same interface, either typed tests or +value-parameterized tests can get it done. It's really up to you the user to +decide which is more convenient for you, depending on your particular case. Some +rough guidelines: -It's difficult to write thread-safe code. Most tests are not written -with thread-safety in mind, and thus may not work correctly in a -multi-threaded setting. +* Typed tests can be easier to write if instances of the different + implementations can be created the same way, modulo the type. For example, + if all these implementations have a public default constructor (such that + you can write `new TypeParam`), or if their factory functions have the same + form (e.g. `CreateInstance<TypeParam>()`). +* Value-parameterized tests can be easier to write if you need different code + patterns to create different implementations' instances, e.g. `new Foo` vs + `new Bar(5)`. To accommodate for the differences, you can write factory + function wrappers and pass these function pointers to the tests as their + parameters. +* When a typed test fails, the output includes the name of the type, which can + help you quickly identify which implementation is wrong. Value-parameterized + tests cannot do this, so there you'll have to look at the iteration number + to know which implementation the failure is from, which is less direct. +* If you make a mistake writing a typed test, the compiler errors can be + harder to digest, as the code is templatized. +* When using typed tests, you need to make sure you are testing against the + interface type, not the concrete types (in other words, you want to make + sure `implicit_cast<MyInterface*>(my_concrete_impl)` works, not just that + `my_concrete_impl` works). It's less likely to make mistakes in this area + when using value-parameterized tests. -If you think about it, it's already hard to make your code work when -you know what other threads are doing. It's much harder, and -sometimes even impossible, to make your code work when you don't know -what other threads are doing (remember that test methods can be added, -deleted, or modified after your test was written). If you want to run -the tests in parallel, you'd better run them in different processes. +I hope I didn't confuse you more. :-) If you don't mind, I'd suggest you to give +both approaches a try. Practice is a much better way to grasp the subtle +differences between the two tools. Once you have some concrete experience, you +can much more easily decide which one to use the next time. -## Why aren't Google Test assertions implemented using exceptions? ## +## My death tests became very slow - what happened? -Our original motivation was to be able to use Google Test in projects -that disable exceptions. Later we realized some additional benefits -of this approach: - - 1. Throwing in a destructor is undefined behavior in C++. Not using exceptions means Google Test's assertions are safe to use in destructors. - 1. The `EXPECT_*` family of macros will continue even after a failure, allowing multiple failures in a `TEST` to be reported in a single run. This is a popular feature, as in C++ the edit-compile-test cycle is usually quite long and being able to fixing more than one thing at a time is a blessing. - 1. If assertions are implemented using exceptions, a test may falsely ignore a failure if it's caught by user code: -```c++ -try { ... ASSERT_TRUE(...) ... } -catch (...) { ... } -``` -The above code will pass even if the `ASSERT_TRUE` throws. While it's unlikely for someone to write this in a test, it's possible to run into this pattern when you write assertions in callbacks that are called by the code under test. +In August 2008 we had to switch the default death test style from `fast` to +`threadsafe`, as the former is no longer safe now that threaded logging is the +default. This caused many death tests to slow down. Unfortunately this change +was necessary. -The downside of not using exceptions is that `ASSERT_*` (implemented -using `return`) will only abort the current function, not the current -`TEST`. +Please read [Fixing Failing Death Tests](death_test_styles.md) for what you can +do. -## Why do we use two different macros for tests with and without fixtures? ## +## I got some run-time errors about invalid proto descriptors when using `ProtocolMessageEquals`. Help! -Unfortunately, C++'s macro system doesn't allow us to use the same -macro for both cases. One possibility is to provide only one macro -for tests with fixtures, and require the user to define an empty -fixture sometimes: +**Note:** `ProtocolMessageEquals` and `ProtocolMessageEquiv` are *deprecated* +now. Please use `EqualsProto`, etc instead. -```c++ -class FooTest : public ::testing::Test {}; +`ProtocolMessageEquals` and `ProtocolMessageEquiv` were redefined recently and +are now less tolerant on invalid protocol buffer definitions. In particular, if +you have a `foo.proto` that doesn't fully qualify the type of a protocol message +it references (e.g. `message<Bar>` where it should be `message<blah.Bar>`), you +will now get run-time errors like: -TEST_F(FooTest, DoesThis) { ... } ``` -or -```c++ -typedef ::testing::Test FooTest; - -TEST_F(FooTest, DoesThat) { ... } +... descriptor.cc:...] Invalid proto descriptor for file "path/to/foo.proto": +... descriptor.cc:...] blah.MyMessage.my_field: ".Bar" is not defined. ``` -Yet, many people think this is one line too many. :-) Our goal was to -make it really easy to write tests, so we tried to make simple tests -trivial to create. That means using a separate macro for such tests. +If you see this, your `.proto` file is broken and needs to be fixed by making +the types fully qualified. The new definition of `ProtocolMessageEquals` and +`ProtocolMessageEquiv` just happen to reveal your bug. -We think neither approach is ideal, yet either of them is reasonable. -In the end, it probably doesn't matter much either way. +## My death test modifies some state, but the change seems lost after the death test finishes. Why? -## Why don't we use structs as test fixtures? ## +Death tests (`EXPECT_DEATH`, etc) are executed in a sub-process s.t. the +expected crash won't kill the test program (i.e. the parent process). As a +result, any in-memory side effects they incur are observable in their respective +sub-processes, but not in the parent process. You can think of them as running +in a parallel universe, more or less. -We like to use structs only when representing passive data. This -distinction between structs and classes is good for documenting the -intent of the code's author. Since test fixtures have logic like -`SetUp()` and `TearDown()`, they are better defined as classes. +In particular, if you use [gMock](../../googlemock) and the death test statement +invokes some mock methods, the parent process will think the calls have never +occurred. Therefore, you may want to move your `EXPECT_CALL` statements inside +the `EXPECT_DEATH` macro. -## Why are death tests implemented as assertions instead of using a test runner? ## +## EXPECT_EQ(htonl(blah), blah_blah) generates weird compiler errors in opt mode. Is this a googletest bug? -Our goal was to make death tests as convenient for a user as C++ -possibly allows. In particular: +Actually, the bug is in `htonl()`. - * The runner-style requires to split the information into two pieces: the definition of the death test itself, and the specification for the runner on how to run the death test and what to expect. The death test would be written in C++, while the runner spec may or may not be. A user needs to carefully keep the two in sync. `ASSERT_DEATH(statement, expected_message)` specifies all necessary information in one place, in one language, without boilerplate code. It is very declarative. - * `ASSERT_DEATH` has a similar syntax and error-reporting semantics as other Google Test assertions, and thus is easy to learn. - * `ASSERT_DEATH` can be mixed with other assertions and other logic at your will. You are not limited to one death test per test method. For example, you can write something like: -```c++ - if (FooCondition()) { - ASSERT_DEATH(Bar(), "blah"); - } else { - ASSERT_EQ(5, Bar()); - } -``` -If you prefer one death test per test method, you can write your tests in that style too, but we don't want to impose that on the users. The fewer artificial limitations the better. - * `ASSERT_DEATH` can reference local variables in the current function, and you can decide how many death tests you want based on run-time information. For example, -```c++ - const int count = GetCount(); // Only known at run time. - for (int i = 1; i <= count; i++) { - ASSERT_DEATH({ - double* buffer = new double[i]; - ... initializes buffer ... - Foo(buffer, i) - }, "blah blah"); - } -``` -The runner-based approach tends to be more static and less flexible, or requires more user effort to get this kind of flexibility. +According to `'man htonl'`, `htonl()` is a *function*, which means it's valid to +use `htonl` as a function pointer. However, in opt mode `htonl()` is defined as +a *macro*, which breaks this usage. -Another interesting thing about `ASSERT_DEATH` is that it calls `fork()` -to create a child process to run the death test. This is lightening -fast, as `fork()` uses copy-on-write pages and incurs almost zero -overhead, and the child process starts from the user-supplied -statement directly, skipping all global and local initialization and -any code leading to the given statement. If you launch the child -process from scratch, it can take seconds just to load everything and -start running if the test links to many libraries dynamically. +Worse, the macro definition of `htonl()` uses a `gcc` extension and is *not* +standard C++. That hacky implementation has some ad hoc limitations. In +particular, it prevents you from writing `Foo<sizeof(htonl(x))>()`, where `Foo` +is a template that has an integral argument. -## My death test modifies some state, but the change seems lost after the death test finishes. Why? ## +The implementation of `EXPECT_EQ(a, b)` uses `sizeof(... a ...)` inside a +template argument, and thus doesn't compile in opt mode when `a` contains a call +to `htonl()`. It is difficult to make `EXPECT_EQ` bypass the `htonl()` bug, as +the solution must work with different compilers on various platforms. -Death tests (`EXPECT_DEATH`, etc) are executed in a sub-process s.t. the -expected crash won't kill the test program (i.e. the parent process). As a -result, any in-memory side effects they incur are observable in their -respective sub-processes, but not in the parent process. You can think of them -as running in a parallel universe, more or less. +`htonl()` has some other problems as described in `//util/endian/endian.h`, +which defines `ghtonl()` to replace it. `ghtonl()` does the same thing `htonl()` +does, only without its problems. We suggest you to use `ghtonl()` instead of +`htonl()`, both in your tests and production code. + +`//util/endian/endian.h` also defines `ghtons()`, which solves similar problems +in `htons()`. -## The compiler complains about "undefined references" to some static const member variables, but I did define them in the class body. What's wrong? ## +Don't forget to add `//util/endian` to the list of dependencies in the `BUILD` +file wherever `ghtonl()` and `ghtons()` are used. The library consists of a +single header file and will not bloat your binary. + +## The compiler complains about "undefined references" to some static const member variables, but I did define them in the class body. What's wrong? If your class has a static data member: @@ -343,23 +209,18 @@ class Foo { }; ``` -You also need to define it _outside_ of the class body in `foo.cc`: +You also need to define it *outside* of the class body in `foo.cc`: ```c++ const int Foo::kBar; // No initializer here. ``` Otherwise your code is **invalid C++**, and may break in unexpected ways. In -particular, using it in Google Test comparison assertions (`EXPECT_EQ`, etc) -will generate an "undefined reference" linker error. - -## I have an interface that has several implementations. Can I write a set of tests once and repeat them over all the implementations? ## - -Google Test doesn't yet have good support for this kind of tests, or -data-driven tests in general. We hope to be able to make improvements in this -area soon. +particular, using it in googletest comparison assertions (`EXPECT_EQ`, etc) will +generate an "undefined reference" linker error. The fact that "it used to work" +doesn't mean it's valid. It just means that you were lucky. :-) -## Can I derive a test fixture from another? ## +## Can I derive a test fixture from another? Yes. @@ -369,33 +230,35 @@ cases may want to use the same or slightly different fixtures. For example, you may want to make sure that all of a GUI library's test cases don't leak important system resources like fonts and brushes. -In Google Test, you share a fixture among test cases by putting the shared -logic in a base test fixture, then deriving from that base a separate fixture -for each test case that wants to use this common logic. You then use `TEST_F()` -to write tests using each derived fixture. +In googletest, you share a fixture among test cases by putting the shared logic +in a base test fixture, then deriving from that base a separate fixture for each +test case that wants to use this common logic. You then use `TEST_F()` to write +tests using each derived fixture. Typically, your code looks like this: ```c++ // Defines a base test fixture. class BaseTest : public ::testing::Test { - protected: - ... + protected: + ... }; // Derives a fixture FooTest from BaseTest. class FooTest : public BaseTest { - protected: - virtual void SetUp() { - BaseTest::SetUp(); // Sets up the base fixture first. - ... additional set-up work ... - } - virtual void TearDown() { - ... clean-up work for FooTest ... - BaseTest::TearDown(); // Remember to tear down the base fixture - // after cleaning up FooTest! - } - ... functions and variables for FooTest ... + protected: + void SetUp() override { + BaseTest::SetUp(); // Sets up the base fixture first. + ... additional set-up work ... + } + + void TearDown() override { + ... clean-up work for FooTest ... + BaseTest::TearDown(); // Remember to tear down the base fixture + // after cleaning up FooTest! + } + + ... functions and variables for FooTest ... }; // Tests that use the fixture FooTest. @@ -406,32 +269,35 @@ TEST_F(FooTest, Baz) { ... } ``` If necessary, you can continue to derive test fixtures from a derived fixture. -Google Test has no limit on how deep the hierarchy can be. +googletest has no limit on how deep the hierarchy can be. -For a complete example using derived test fixtures, see -[sample5](../samples/sample5_unittest.cc). +For a complete example using derived test fixtures, see [googletest +sample](https://github.com/google/googletest/blob/master/googletest/samples/sample5_unittest.cc) -## My compiler complains "void value not ignored as it ought to be." What does this mean? ## +## My compiler complains "void value not ignored as it ought to be." What does this mean? You're probably using an `ASSERT_*()` in a function that doesn't return `void`. -`ASSERT_*()` can only be used in `void` functions. +`ASSERT_*()` can only be used in `void` functions, due to exceptions being +disabled by our build system. Please see more details +[here](advanced.md#assertion-placement). -## My death test hangs (or seg-faults). How do I fix it? ## +## My death test hangs (or seg-faults). How do I fix it? -In Google Test, death tests are run in a child process and the way they work is +In googletest, death tests are run in a child process and the way they work is delicate. To write death tests you really need to understand how they work. -Please make sure you have read this. +Please make sure you have read [this](advanced.md#how-it-works). In particular, death tests don't like having multiple threads in the parent -process. So the first thing you can try is to eliminate creating threads -outside of `EXPECT_DEATH()`. +process. So the first thing you can try is to eliminate creating threads outside +of `EXPECT_DEATH()`. For example, you may want to use [mocks](../../googlemock) +or fake objects instead of real ones in your tests. Sometimes this is impossible as some library you must use may be creating threads before `main()` is even reached. In this case, you can try to minimize the chance of conflicts by either moving as many activities as possible inside `EXPECT_DEATH()` (in the extreme case, you want to move everything inside), or -leaving as few things as possible in it. Also, you can try to set the death -test style to `"threadsafe"`, which is safer but slower, and see if it helps. +leaving as few things as possible in it. Also, you can try to set the death test +style to `"threadsafe"`, which is safer but slower, and see if it helps. If you go with thread-safe death tests, remember that they rerun the test program from the beginning in the child process. Therefore make sure your @@ -441,28 +307,52 @@ In the end, this boils down to good concurrent programming. You have to make sure that there is no race conditions or dead locks in your program. No silver bullet - sorry! -## Should I use the constructor/destructor of the test fixture or the set-up/tear-down function? ## +## Should I use the constructor/destructor of the test fixture or SetUp()/TearDown()? -The first thing to remember is that Google Test does not reuse the -same test fixture object across multiple tests. For each `TEST_F`, -Google Test will create a fresh test fixture object, _immediately_ -call `SetUp()`, run the test body, call `TearDown()`, and then -_immediately_ delete the test fixture object. +The first thing to remember is that googletest does **not** reuse the same test +fixture object across multiple tests. For each `TEST_F`, googletest will create +a **fresh** test fixture object, immediately call `SetUp()`, run the test body, +call `TearDown()`, and then delete the test fixture object. -When you need to write per-test set-up and tear-down logic, you have -the choice between using the test fixture constructor/destructor or -`SetUp()/TearDown()`. The former is usually preferred, as it has the -following benefits: +When you need to write per-test set-up and tear-down logic, you have the choice +between using the test fixture constructor/destructor or `SetUp()/TearDown()`. +The former is usually preferred, as it has the following benefits: - * By initializing a member variable in the constructor, we have the option to make it `const`, which helps prevent accidental changes to its value and makes the tests more obviously correct. - * In case we need to subclass the test fixture class, the subclass' constructor is guaranteed to call the base class' constructor first, and the subclass' destructor is guaranteed to call the base class' destructor afterward. With `SetUp()/TearDown()`, a subclass may make the mistake of forgetting to call the base class' `SetUp()/TearDown()` or call them at the wrong moment. +* By initializing a member variable in the constructor, we have the option to + make it `const`, which helps prevent accidental changes to its value and + makes the tests more obviously correct. +* In case we need to subclass the test fixture class, the subclass' + constructor is guaranteed to call the base class' constructor *first*, and + the subclass' destructor is guaranteed to call the base class' destructor + *afterward*. With `SetUp()/TearDown()`, a subclass may make the mistake of + forgetting to call the base class' `SetUp()/TearDown()` or call them at the + wrong time. You may still want to use `SetUp()/TearDown()` in the following rare cases: - * If the tear-down operation could throw an exception, you must use `TearDown()` as opposed to the destructor, as throwing in a destructor leads to undefined behavior and usually will kill your program right away. Note that many standard libraries (like STL) may throw when exceptions are enabled in the compiler. Therefore you should prefer `TearDown()` if you want to write portable tests that work with or without exceptions. - * The assertion macros throw an exception when flag `--gtest_throw_on_failure` is specified. Therefore, you shouldn't use Google Test assertions in a destructor if you plan to run your tests with this flag. - * In a constructor or destructor, you cannot make a virtual function call on this object. (You can call a method declared as virtual, but it will be statically bound.) Therefore, if you need to call a method that will be overridden in a derived class, you have to use `SetUp()/TearDown()`. -## The compiler complains "no matching function to call" when I use ASSERT\_PREDn. How do I fix it? ## +* In the body of a constructor (or destructor), it's not possible to use the + `ASSERT_xx` macros. Therefore, if the set-up operation could cause a fatal + test failure that should prevent the test from running, it's necessary to + use a `CHECK` macro or to use `SetUp()` instead of a constructor. +* If the tear-down operation could throw an exception, you must use + `TearDown()` as opposed to the destructor, as throwing in a destructor leads + to undefined behavior and usually will kill your program right away. Note + that many standard libraries (like STL) may throw when exceptions are + enabled in the compiler. Therefore you should prefer `TearDown()` if you + want to write portable tests that work with or without exceptions. +* The googletest team is considering making the assertion macros throw on + platforms where exceptions are enabled (e.g. Windows, Mac OS, and Linux + client-side), which will eliminate the need for the user to propagate + failures from a subroutine to its caller. Therefore, you shouldn't use + googletest assertions in a destructor if your code could run on such a + platform. +* In a constructor or destructor, you cannot make a virtual function call on + this object. (You can call a method declared as virtual, but it will be + statically bound.) Therefore, if you need to call a method that will be + overridden in a derived class, you have to use `SetUp()/TearDown()`. + + +## The compiler complains "no matching function to call" when I use ASSERT_PRED*. How do I fix it? If the predicate function you use in `ASSERT_PRED*` or `EXPECT_PRED*` is overloaded or a template, the compiler will have trouble figuring out which @@ -480,6 +370,7 @@ For example, suppose you have bool IsPositive(int n) { return n > 0; } + bool IsPositive(double x) { return x > 0; } @@ -497,8 +388,8 @@ However, this will work: EXPECT_PRED1(static_cast<bool (*)(int)>(IsPositive), 5); ``` -(The stuff inside the angled brackets for the `static_cast` operator is the -type of the function pointer for the `int`-version of `IsPositive()`.) +(The stuff inside the angled brackets for the `static_cast` operator is the type +of the function pointer for the `int`-version of `IsPositive()`.) As another example, when you have a template function @@ -522,72 +413,76 @@ following won't compile: ASSERT_PRED2(GreaterThan<int, int>, 5, 0); ``` - -as the C++ pre-processor thinks you are giving `ASSERT_PRED2` 4 arguments, -which is one more than expected. The workaround is to wrap the predicate -function in parentheses: +as the C++ pre-processor thinks you are giving `ASSERT_PRED2` 4 arguments, which +is one more than expected. The workaround is to wrap the predicate function in +parentheses: ```c++ ASSERT_PRED2((GreaterThan<int, int>), 5, 0); ``` -## My compiler complains about "ignoring return value" when I call RUN\_ALL\_TESTS(). Why? ## +## My compiler complains about "ignoring return value" when I call RUN_ALL_TESTS(). Why? Some people had been ignoring the return value of `RUN_ALL_TESTS()`. That is, instead of ```c++ -return RUN_ALL_TESTS(); + return RUN_ALL_TESTS(); ``` they write ```c++ -RUN_ALL_TESTS(); + RUN_ALL_TESTS(); ``` -This is wrong and dangerous. A test runner needs to see the return value of -`RUN_ALL_TESTS()` in order to determine if a test has passed. If your `main()` -function ignores it, your test will be considered successful even if it has a -Google Test assertion failure. Very bad. +This is **wrong and dangerous**. The testing services needs to see the return +value of `RUN_ALL_TESTS()` in order to determine if a test has passed. If your +`main()` function ignores it, your test will be considered successful even if it +has a googletest assertion failure. Very bad. -To help the users avoid this dangerous bug, the implementation of -`RUN_ALL_TESTS()` causes gcc to raise this warning, when the return value is -ignored. If you see this warning, the fix is simple: just make sure its value -is used as the return value of `main()`. +We have decided to fix this (thanks to Michael Chastain for the idea). Now, your +code will no longer be able to ignore `RUN_ALL_TESTS()` when compiled with +`gcc`. If you do so, you'll get a compiler error. -## My compiler complains that a constructor (or destructor) cannot return a value. What's going on? ## +If you see the compiler complaining about you ignoring the return value of +`RUN_ALL_TESTS()`, the fix is simple: just make sure its value is used as the +return value of `main()`. + +But how could we introduce a change that breaks existing tests? Well, in this +case, the code was already broken in the first place, so we didn't break it. :-) + +## My compiler complains that a constructor (or destructor) cannot return a value. What's going on? Due to a peculiarity of C++, in order to support the syntax for streaming messages to an `ASSERT_*`, e.g. ```c++ -ASSERT_EQ(1, Foo()) << "blah blah" << foo; + ASSERT_EQ(1, Foo()) << "blah blah" << foo; ``` we had to give up using `ASSERT*` and `FAIL*` (but not `EXPECT*` and `ADD_FAILURE*`) in constructors and destructors. The workaround is to move the content of your constructor/destructor to a private void member function, or -switch to `EXPECT_*()` if that works. This section in the user's guide explains -it. +switch to `EXPECT_*()` if that works. This +[section](advanced.md#assertion-placement) in the user's guide explains it. -## My set-up function is not called. Why? ## +## My SetUp() function is not called. Why? -C++ is case-sensitive. It should be spelled as `SetUp()`. Did you -spell it as `Setup()`? +C++ is case-sensitive. Did you spell it as `Setup()`? Similarly, sometimes people spell `SetUpTestCase()` as `SetupTestCase()` and wonder why it's never called. -## How do I jump to the line of a failure in Emacs directly? ## +## How do I jump to the line of a failure in Emacs directly? + +googletest's failure message format is understood by Emacs and many other IDEs, +like acme and XCode. If a googletest message is in a compilation buffer in +Emacs, then it's clickable. -Google Test's failure message format is understood by Emacs and many other -IDEs, like acme and XCode. If a Google Test message is in a compilation buffer -in Emacs, then it's clickable. You can now hit `enter` on a message to jump to -the corresponding source code, or use `C-x `` to jump to the next failure. -## I have several test cases which share the same test fixture logic, do I have to define a new test fixture class for each of them? This seems pretty tedious. ## +## I have several test cases which share the same test fixture logic, do I have to define a new test fixture class for each of them? This seems pretty tedious. You don't have to. Instead of @@ -604,6 +499,7 @@ TEST_F(BarTest, Def) { ... } ``` you can simply `typedef` the test fixtures: + ```c++ typedef BaseTest FooTest; @@ -616,192 +512,47 @@ TEST_F(BarTest, Abc) { ... } TEST_F(BarTest, Def) { ... } ``` -## The Google Test output is buried in a whole bunch of log messages. What do I do? ## +## googletest output is buried in a whole bunch of LOG messages. What do I do? -The Google Test output is meant to be a concise and human-friendly report. If -your test generates textual output itself, it will mix with the Google Test +The googletest output is meant to be a concise and human-friendly report. If +your test generates textual output itself, it will mix with the googletest output, making it hard to read. However, there is an easy solution to this problem. -Since most log messages go to stderr, we decided to let Google Test output go -to stdout. This way, you can easily separate the two using redirection. For +Since `LOG` messages go to stderr, we decided to let googletest output go to +stdout. This way, you can easily separate the two using redirection. For example: -``` -./my_test > googletest_output.txt -``` - -## Why should I prefer test fixtures over global variables? ## - -There are several good reasons: - 1. It's likely your test needs to change the states of its global variables. This makes it difficult to keep side effects from escaping one test and contaminating others, making debugging difficult. By using fixtures, each test has a fresh set of variables that's different (but with the same names). Thus, tests are kept independent of each other. - 1. Global variables pollute the global namespace. - 1. Test fixtures can be reused via subclassing, which cannot be done easily with global variables. This is useful if many test cases have something in common. - -## How do I test private class members without writing FRIEND\_TEST()s? ## -You should try to write testable code, which means classes should be easily -tested from their public interface. One way to achieve this is the Pimpl idiom: -you move all private members of a class into a helper class, and make all -members of the helper class public. - -You have several other options that don't require using `FRIEND_TEST`: - * Write the tests as members of the fixture class: -```c++ -class Foo { - friend class FooTest; - ... -}; - -class FooTest : public ::testing::Test { - protected: - ... - void Test1() {...} // This accesses private members of class Foo. - void Test2() {...} // So does this one. -}; - -TEST_F(FooTest, Test1) { - Test1(); -} - -TEST_F(FooTest, Test2) { - Test2(); -} +```shell +$ ./my_test > gtest_output.txt ``` - * In the fixture class, write accessors for the tested class' private members, then use the accessors in your tests: -```c++ -class Foo { - friend class FooTest; - ... -}; -class FooTest : public ::testing::Test { - protected: - ... - T1 get_private_member1(Foo* obj) { - return obj->private_member1_; - } -}; -TEST_F(FooTest, Test1) { - ... - get_private_member1(x) - ... -} -``` - * If the methods are declared **protected**, you can change their access level in a test-only subclass: -```c++ -class YourClass { - ... - protected: // protected access for testability. - int DoSomethingReturningInt(); - ... -}; - -// in the your_class_test.cc file: -class TestableYourClass : public YourClass { - ... - public: using YourClass::DoSomethingReturningInt; // changes access rights - ... -}; - -TEST_F(YourClassTest, DoSomethingTest) { - TestableYourClass obj; - assertEquals(expected_value, obj.DoSomethingReturningInt()); -} -``` - -## How do I test private class static members without writing FRIEND\_TEST()s? ## - -We find private static methods clutter the header file. They are -implementation details and ideally should be kept out of a .h. So often I make -them free functions instead. - -Instead of: -```c++ -// foo.h -class Foo { - ... - private: - static bool Func(int n); -}; - -// foo.cc -bool Foo::Func(int n) { ... } - -// foo_test.cc -EXPECT_TRUE(Foo::Func(12345)); -``` - -You probably should better write: -```c++ -// foo.h -class Foo { - ... -}; - -// foo.cc -namespace internal { - bool Func(int n) { ... } -} - -// foo_test.cc -namespace internal { - bool Func(int n); -} - -EXPECT_TRUE(internal::Func(12345)); -``` - -## I would like to run a test several times with different parameters. Do I need to write several similar copies of it? ## - -No. You can use a feature called [value-parameterized tests](advanced.md#Value_Parameterized_Tests) which -lets you repeat your tests with different parameters, without defining it more than once. - -## How do I test a file that defines main()? ## - -To test a `foo.cc` file, you need to compile and link it into your unit test -program. However, when the file contains a definition for the `main()` -function, it will clash with the `main()` of your unit test, and will result in -a build error. +## Why should I prefer test fixtures over global variables? -The right solution is to split it into three files: - 1. `foo.h` which contains the declarations, - 1. `foo.cc` which contains the definitions except `main()`, and - 1. `foo_main.cc` which contains nothing but the definition of `main()`. - -Then `foo.cc` can be easily tested. - -If you are adding tests to an existing file and don't want an intrusive change -like this, there is a hack: just include the entire `foo.cc` file in your unit -test. For example: -```c++ -// File foo_unittest.cc - -// The headers section -... - -// Renames main() in foo.cc to make room for the unit test main() -#define main FooMain - -#include "a/b/foo.cc" - -// The tests start here. -... -``` +There are several good reasons: +1. It's likely your test needs to change the states of its global variables. + This makes it difficult to keep side effects from escaping one test and + contaminating others, making debugging difficult. By using fixtures, each + test has a fresh set of variables that's different (but with the same + names). Thus, tests are kept independent of each other. +1. Global variables pollute the global namespace. +1. Test fixtures can be reused via subclassing, which cannot be done easily + with global variables. This is useful if many test cases have something in + common. -However, please remember this is a hack and should only be used as the last -resort. -## What can the statement argument in ASSERT\_DEATH() be? ## + ## What can the statement argument in ASSERT_DEATH() be? -`ASSERT_DEATH(_statement_, _regex_)` (or any death assertion macro) can be used -wherever `_statement_` is valid. So basically `_statement_` can be any C++ +`ASSERT_DEATH(*statement*, *regex*)` (or any death assertion macro) can be used +wherever `*statement*` is valid. So basically `*statement*` can be any C++ statement that makes sense in the current context. In particular, it can reference global and/or local variables, and can be: - * a simple function call (often the case), - * a complex expression, or - * a compound statement. + +* a simple function call (often the case), +* a complex expression, or +* a compound statement. Some examples are shown here: @@ -818,7 +569,7 @@ TEST(MyDeathTest, ComplexExpression) { "(Func1|Method) failed"); } -// Death assertions can be used any where in a function. In +// Death assertions can be used any where in a function. In // particular, they can be inside a loop. TEST(MyDeathTest, InsideLoop) { // Verifies that Foo(0), Foo(1), ..., and Foo(4) all die. @@ -837,49 +588,47 @@ TEST(MyDeathTest, CompoundStatement) { Bar(i); } }, - "Bar has \\d+ errors");} + "Bar has \\d+ errors"); +} ``` -`googletest_unittest.cc` contains more examples if you are interested. - -## What syntax does the regular expression in ASSERT\_DEATH use? ## +gtest-death-test_test.cc contains more examples if you are interested. -On POSIX systems, Google Test uses the POSIX Extended regular -expression syntax -(http://en.wikipedia.org/wiki/Regular_expression#POSIX_Extended_Regular_Expressions). -On Windows, it uses a limited variant of regular expression -syntax. For more details, see the -[regular expression syntax](advanced.md#Regular_Expression_Syntax). +## I have a fixture class `FooTest`, but `TEST_F(FooTest, Bar)` gives me error ``"no matching function for call to `FooTest::FooTest()'"``. Why? -## I have a fixture class Foo, but TEST\_F(Foo, Bar) gives me error "no matching function for call to Foo::Foo()". Why? ## +Googletest needs to be able to create objects of your test fixture class, so it +must have a default constructor. Normally the compiler will define one for you. +However, there are cases where you have to define your own: -Google Test needs to be able to create objects of your test fixture class, so -it must have a default constructor. Normally the compiler will define one for -you. However, there are cases where you have to define your own: - * If you explicitly declare a non-default constructor for class `Foo`, then you need to define a default constructor, even if it would be empty. - * If `Foo` has a const non-static data member, then you have to define the default constructor _and_ initialize the const member in the initializer list of the constructor. (Early versions of `gcc` doesn't force you to initialize the const member. It's a bug that has been fixed in `gcc 4`.) +* If you explicitly declare a non-default constructor for class `FooTest` + (`DISALLOW_EVIL_CONSTRUCTORS()` does this), then you need to define a + default constructor, even if it would be empty. +* If `FooTest` has a const non-static data member, then you have to define the + default constructor *and* initialize the const member in the initializer + list of the constructor. (Early versions of `gcc` doesn't force you to + initialize the const member. It's a bug that has been fixed in `gcc 4`.) -## Why does ASSERT\_DEATH complain about previous threads that were already joined? ## +## Why does ASSERT_DEATH complain about previous threads that were already joined? -With the Linux pthread library, there is no turning back once you cross the -line from single thread to multiple threads. The first time you create a -thread, a manager thread is created in addition, so you get 3, not 2, threads. -Later when the thread you create joins the main thread, the thread count -decrements by 1, but the manager thread will never be killed, so you still have -2 threads, which means you cannot safely run a death test. +With the Linux pthread library, there is no turning back once you cross the line +from single thread to multiple threads. The first time you create a thread, a +manager thread is created in addition, so you get 3, not 2, threads. Later when +the thread you create joins the main thread, the thread count decrements by 1, +but the manager thread will never be killed, so you still have 2 threads, which +means you cannot safely run a death test. The new NPTL thread library doesn't suffer from this problem, as it doesn't create a manager thread. However, if you don't control which machine your test runs on, you shouldn't depend on this. -## Why does Google Test require the entire test case, instead of individual tests, to be named FOODeathTest when it uses ASSERT\_DEATH? ## +## Why does googletest require the entire test case, instead of individual tests, to be named *DeathTest when it uses ASSERT_DEATH? -Google Test does not interleave tests from different test cases. That is, it -runs all tests in one test case first, and then runs all tests in the next test -case, and so on. Google Test does this because it needs to set up a test case -before the first test in it is run, and tear it down afterwords. Splitting up -the test case would require multiple set-up and tear-down processes, which is -inefficient and makes the semantics unclean. +googletest does not interleave tests from different test cases. That is, it runs +all tests in one test case first, and then runs all tests in the next test case, +and so on. googletest does this because it needs to set up a test case before +the first test in it is run, and tear it down afterwords. Splitting up the test +case would require multiple set-up and tear-down processes, which is inefficient +and makes the semantics unclean. If we were to determine the order of tests based on test name instead of test case name, then we would have a problem with the following situation: @@ -897,7 +646,7 @@ interleave tests from different test cases, we need to run all tests in the `FooTest` case before running any test in the `BarTest` case. This contradicts with the requirement to run `BarTest.DefDeathTest` before `FooTest.Uvw`. -## But I don't like calling my entire test case FOODeathTest when it contains both death tests and non-death tests. What do I do? ## +## But I don't like calling my entire test case \*DeathTest when it contains both death tests and non-death tests. What do I do? You don't have to, but if you like, you may split up the test case into `FooTest` and `FooDeathTest`, where the names make it clear that they are @@ -909,119 +658,82 @@ class FooTest : public ::testing::Test { ... }; TEST_F(FooTest, Abc) { ... } TEST_F(FooTest, Def) { ... } -typedef FooTest FooDeathTest; +using FooDeathTest = FooTest; TEST_F(FooDeathTest, Uvw) { ... EXPECT_DEATH(...) ... } TEST_F(FooDeathTest, Xyz) { ... ASSERT_DEATH(...) ... } ``` -## The compiler complains about "no match for 'operator<<'" when I use an assertion. What gives? ## +## googletest prints the LOG messages in a death test's child process only when the test fails. How can I see the LOG messages when the death test succeeds? + +Printing the LOG messages generated by the statement inside `EXPECT_DEATH()` +makes it harder to search for real problems in the parent's log. Therefore, +googletest only prints them when the death test has failed. + +If you really need to see such LOG messages, a workaround is to temporarily +break the death test (e.g. by changing the regex pattern it is expected to +match). Admittedly, this is a hack. We'll consider a more permanent solution +after the fork-and-exec-style death tests are implemented. + +## The compiler complains about "no match for 'operator<<'" when I use an assertion. What gives? If you use a user-defined type `FooType` in an assertion, you must make sure there is an `std::ostream& operator<<(std::ostream&, const FooType&)` function defined such that we can print a value of `FooType`. In addition, if `FooType` is declared in a name space, the `<<` operator also -needs to be defined in the _same_ name space. +needs to be defined in the *same* name space. See go/totw/49 for details. -## How do I suppress the memory leak messages on Windows? ## +## How do I suppress the memory leak messages on Windows? -Since the statically initialized Google Test singleton requires allocations on +Since the statically initialized googletest singleton requires allocations on the heap, the Visual C++ memory leak detector will report memory leaks at the end of the program run. The easiest way to avoid this is to use the `_CrtMemCheckpoint` and `_CrtMemDumpAllObjectsSince` calls to not report any statically initialized heap objects. See MSDN for more details and additional heap check/debug routines. -## I am building my project with Google Test in Visual Studio and all I'm getting is a bunch of linker errors (or warnings). Help! ## - -You may get a number of the following linker error or warnings if you -attempt to link your test project with the Google Test library when -your project and the are not built using the same compiler settings. - - * LNK2005: symbol already defined in object - * LNK4217: locally defined symbol 'symbol' imported in function 'function' - * LNK4049: locally defined symbol 'symbol' imported - -The Google Test project (gtest.vcproj) has the Runtime Library option -set to /MT (use multi-threaded static libraries, /MTd for debug). If -your project uses something else, for example /MD (use multi-threaded -DLLs, /MDd for debug), you need to change the setting in the Google -Test project to match your project's. - -To update this setting open the project properties in the Visual -Studio IDE then select the branch Configuration Properties | C/C++ | -Code Generation and change the option "Runtime Library". You may also try -using gtest-md.vcproj instead of gtest.vcproj. - -## I put my tests in a library and Google Test doesn't run them. What's happening? ## -Have you read a -[warning](primer.md#important-note-for-visual-c-users) on -the Google Test Primer page? - -## I want to use Google Test with Visual Studio but don't know where to start. ## -Many people are in your position and one of them posted his solution to our mailing list. - -## I am seeing compile errors mentioning std::type\_traits when I try to use Google Test on Solaris. ## -Google Test uses parts of the standard C++ library that SunStudio does not support. -Our users reported success using alternative implementations. Try running the build after running this command: - -`export CC=cc CXX=CC CXXFLAGS='-library=stlport4'` - -## How can my code detect if it is running in a test? ## - -If you write code that sniffs whether it's running in a test and does -different things accordingly, you are leaking test-only logic into -production code and there is no easy way to ensure that the test-only -code paths aren't run by mistake in production. Such cleverness also -leads to -[Heisenbugs](http://en.wikipedia.org/wiki/Unusual_software_bug#Heisenbug). -Therefore we strongly advise against the practice, and Google Test doesn't -provide a way to do it. - -In general, the recommended way to cause the code to behave -differently under test is [dependency injection](http://jamesshore.com/Blog/Dependency-Injection-Demystified.html). -You can inject different functionality from the test and from the -production code. Since your production code doesn't link in the -for-test logic at all, there is no danger in accidentally running it. - -However, if you _really_, _really_, _really_ have no choice, and if -you follow the rule of ending your test program names with `_test`, -you can use the _horrible_ hack of sniffing your executable name -(`argv[0]` in `main()`) to know whether the code is under test. - -## Google Test defines a macro that clashes with one defined by another library. How do I deal with that? ## - -In C++, macros don't obey namespaces. Therefore two libraries that -both define a macro of the same name will clash if you `#include` both -definitions. In case a Google Test macro clashes with another -library, you can force Google Test to rename its macro to avoid the -conflict. - -Specifically, if both Google Test and some other code define macro -`FOO`, you can add -``` - -DGTEST_DONT_DEFINE_FOO=1 -``` -to the compiler flags to tell Google Test to change the macro's name -from `FOO` to `GTEST_FOO`. For example, with `-DGTEST_DONT_DEFINE_TEST=1`, you'll need to write -```c++ - GTEST_TEST(SomeTest, DoesThis) { ... } -``` -instead of -```c++ - TEST(SomeTest, DoesThis) { ... } -``` -in order to define a test. -Currently, the following `TEST`, `FAIL`, `SUCCEED`, and the basic comparison assertion macros can have . You can see the full list of covered macros [here](../include/gtest/gtest.h). More information can be found in the "Avoiding Macro Name Clashes" section of the README file. +## How can my code detect if it is running in a test? + +If you write code that sniffs whether it's running in a test and does different +things accordingly, you are leaking test-only logic into production code and +there is no easy way to ensure that the test-only code paths aren't run by +mistake in production. Such cleverness also leads to +[Heisenbugs](https://en.wikipedia.org/wiki/Heisenbug). Therefore we strongly +advise against the practice, and googletest doesn't provide a way to do it. + +In general, the recommended way to cause the code to behave differently under +test is [Dependency Injection](https://en.wikipedia.org/wiki/Dependency_injection). You can inject +different functionality from the test and from the production code. Since your +production code doesn't link in the for-test logic at all (the +[`testonly`](https://docs.bazel.build/versions/master/be/common-definitions.html#common.testonly) +attribute for BUILD targets helps to ensure that), there is no danger in +accidentally running it. +However, if you *really*, *really*, *really* have no choice, and if you follow +the rule of ending your test program names with `_test`, you can use the +*horrible* hack of sniffing your executable name (`argv[0]` in `main()`) to know +whether the code is under test. -## Is it OK if I have two separate `TEST(Foo, Bar)` test methods defined in different namespaces? ## + +## How do I temporarily disable a test? + +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). + +To include disabled tests in test execution, just invoke the test program with +the --gtest_also_run_disabled_tests flag. + +## Is it OK if I have two separate `TEST(Foo, Bar)` test methods defined in different namespaces? Yes. -The rule is **all test methods in the same test case must use the same fixture class**. This means that the following is **allowed** because both tests use the same fixture class (`::testing::Test`). +The rule is **all test methods in the same test case must use the same fixture +class.** This means that the following is **allowed** because both tests use the +same fixture class (`::testing::Test`). ```c++ namespace foo { @@ -1037,7 +749,9 @@ TEST(CoolTest, DoSomething) { } // namespace bar ``` -However, the following code is **not allowed** and will produce a runtime error from Google Test because the test methods are using different test fixture classes with the same test case name. +However, the following code is **not allowed** and will produce a runtime error +from googletest because the test methods are using different test fixture +classes with the same test case name. ```c++ namespace foo { @@ -1054,39 +768,3 @@ TEST_F(CoolTest, DoSomething) { } } // namespace bar ``` - -## How do I build Google Testing Framework with Xcode 4? ## - -If you try to build Google Test's Xcode project with Xcode 4.0 or later, you may encounter an error message that looks like -"Missing SDK in target gtest\_framework: /Developer/SDKs/MacOSX10.4u.sdk". That means that Xcode does not support the SDK the project is targeting. See the Xcode section in the [README](../README.md) file on how to resolve this. - -## How do I easily discover the flags needed for GoogleTest? ## - -GoogleTest (and GoogleMock) now support discovering all necessary flags using pkg-config. -See the [pkg-config guide](Pkgconfig.md) on how you can easily discover all compiler and -linker flags using pkg-config. - -## My question is not covered in your FAQ! ## - -If you cannot find the answer to your question in this FAQ, there are -some other resources you can use: - - 1. read other [wiki pages](../docs), - 1. search the mailing list [archive](https://groups.google.com/forum/#!forum/googletestframework), - 1. ask it on [googletestframework@googlegroups.com](mailto:googletestframework@googlegroups.com) and someone will answer it (to prevent spam, we require you to join the [discussion group](http://groups.google.com/group/googletestframework) before you can post.). - -Please note that creating an issue in the -[issue tracker](https://github.com/google/googletest/issues) is _not_ -a good way to get your answer, as it is monitored infrequently by a -very small number of people. - -When asking a question, it's helpful to provide as much of the -following information as possible (people cannot help you if there's -not enough information in your question): - - * the version (or the commit hash if you check out from Git directly) of Google Test you use (Google Test is under active development, so it's possible that your problem has been solved in a later version), - * your operating system, - * the name and version of your compiler, - * the complete command line flags you give to your compiler, - * the complete compiler error messages (if the question is about compilation), - * the _actual_ code (ideally, a minimal but complete program) that has the problem you encounter. |