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diff --git a/docs/faq.md b/docs/faq.md index 40712321..c7d10b50 100644 --- a/docs/faq.md +++ b/docs/faq.md @@ -1,9 +1,9 @@ -# Googletest FAQ +# GoogleTest FAQ ## Why should test suite names and test names not contain underscore? {: .callout .note} -Note: Googletest reserves underscore (`_`) for special purpose keywords, such as +Note: GoogleTest reserves underscore (`_`) for special-purpose keywords, such as [the `DISABLED_` prefix](advanced.md#temporarily-disabling-tests), in addition to the following rationale. @@ -33,9 +33,9 @@ contains `_`? `TestSuiteName_Bar__Test`, which is invalid. So clearly `TestSuiteName` and `TestName` cannot start or end with `_` -(Actually, `TestSuiteName` 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 `_`.). +(Actually, `TestSuiteName` 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 `TestSuiteName` and `TestName` to contain `_` in the middle. However, consider this: @@ -50,15 +50,15 @@ Now, the two `TEST`s will both generate the same class So for simplicity, we just ask the users to avoid `_` in `TestSuiteName` 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 +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 +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)`? +## 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 `nullptr` with each of these macros, e.g. `EXPECT_EQ(ptr, nullptr)`, `EXPECT_NE(ptr, nullptr)`, `ASSERT_EQ(ptr, nullptr)`, @@ -68,7 +68,7 @@ because `nullptr` does not have the type problems that `NULL` does. 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 +(otherwise we make the implementation of GoogleTest harder to maintain and more error-prone than necessary). Historically, the `EXPECT_EQ()` macro took the *expected* value as its first @@ -128,30 +128,9 @@ 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. -## I got some run-time errors about invalid proto descriptors when using `ProtocolMessageEquals`. Help! - -{: .callout .note} -**Note:** `ProtocolMessageEquals` and `ProtocolMessageEquiv` are *deprecated* -now. Please use `EqualsProto`, etc instead. - -`ProtocolMessageEquals` and `ProtocolMessageEquiv` were redefined recently and -are now less tolerant of 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: - -``` -... descriptor.cc:...] Invalid proto descriptor for file "path/to/foo.proto": -... descriptor.cc:...] blah.MyMessage.my_field: ".Bar" is not defined. -``` - -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. - ## My death test modifies some state, but the change seems lost after the death test finishes. Why? -Death tests (`EXPECT_DEATH`, etc) are executed in a sub-process s.t. the +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 @@ -162,7 +141,7 @@ 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. -## EXPECT_EQ(htonl(blah), blah_blah) generates weird compiler errors in opt mode. Is this a googletest bug? +## EXPECT_EQ(htonl(blah), blah_blah) generates weird compiler errors in opt mode. Is this a GoogleTest bug? Actually, the bug is in `htonl()`. @@ -192,16 +171,16 @@ 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 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. :-) +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. :-) If the declaration of the static data member is `constexpr` then it is implicitly an `inline` definition, and a separate definition in `foo.cc` is not @@ -225,7 +204,7 @@ 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 suites don't leak important system resources like fonts and brushes. -In googletest, you share a fixture among test suites by putting the shared logic +In GoogleTest, you share a fixture among test suites by putting the shared logic in a base test fixture, then deriving from that base a separate fixture for each test suite that wants to use this common logic. You then use `TEST_F()` to write tests using each derived fixture. @@ -264,10 +243,10 @@ TEST_F(FooTest, Baz) { ... } ``` If necessary, you can continue to derive test fixtures from a derived fixture. -googletest 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_unittest.cc](https://github.com/google/googletest/blob/master/googletest/samples/sample5_unittest.cc). +[sample5_unittest.cc](https://github.com/google/googletest/blob/main/googletest/samples/sample5_unittest.cc). ## My compiler complains "void value not ignored as it ought to be." What does this mean? @@ -278,9 +257,10 @@ disabled by our build system. Please see more details ## My death test hangs (or seg-faults). How do I fix it? -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](advanced.md#how-it-works). +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—see +the details at [Death Assertions](reference/assertions.md#death) in the +Assertions Reference. 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 @@ -304,13 +284,13 @@ bullet - sorry! ## Should I use the constructor/destructor of the test fixture or SetUp()/TearDown()? {#CtorVsSetUp} -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 +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()`. +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 @@ -327,7 +307,7 @@ You may still want to use `SetUp()/TearDown()` in the following cases: * C++ does not allow virtual function calls in constructors and destructors. You can call a method declared as virtual, but it will not use dynamic - dispatch, it will use the definition from the class the constructor of which + dispatch. It will use the definition from the class the constructor of which is currently executing. This is because calling a virtual method before the derived class constructor has a chance to run is very dangerous - the virtual method might operate on uninitialized data. Therefore, if you need @@ -344,81 +324,17 @@ You may still want to use `SetUp()/TearDown()` in the following cases: 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 +* 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 + GoogleTest assertions in a destructor if your code could run on such a platform. -## 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 -overloaded version it should use. `ASSERT_PRED_FORMAT*` and -`EXPECT_PRED_FORMAT*` don't have this problem. - -If you see this error, you might want to switch to -`(ASSERT|EXPECT)_PRED_FORMAT*`, which will also give you a better failure -message. If, however, that is not an option, you can resolve the problem by -explicitly telling the compiler which version to pick. - -For example, suppose you have +## The compiler complains "no matching function to call" when I use `ASSERT_PRED*`. How do I fix it? -```c++ -bool IsPositive(int n) { - return n > 0; -} - -bool IsPositive(double x) { - return x > 0; -} -``` - -you will get a compiler error if you write - -```c++ -EXPECT_PRED1(IsPositive, 5); -``` - -However, this will work: - -```c++ -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()`.) - -As another example, when you have a template function - -```c++ -template <typename T> -bool IsNegative(T x) { - return x < 0; -} -``` - -you can use it in a predicate assertion like this: - -```c++ -ASSERT_PRED1(IsNegative<int>, -5); -``` - -Things are more interesting if your template has more than one parameter. The -following won't compile: - -```c++ -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: - -```c++ -ASSERT_PRED2((GreaterThan<int, int>), 5, 0); -``` +See details for [`EXPECT_PRED*`](reference/assertions.md#EXPECT_PRED) in the +Assertions Reference. ## My compiler complains about "ignoring return value" when I call RUN_ALL_TESTS(). Why? @@ -438,7 +354,7 @@ they write 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. +has a GoogleTest assertion failure. Very bad. 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 @@ -473,8 +389,7 @@ C++ is case-sensitive. Did you spell it as `Setup()`? Similarly, sometimes people spell `SetUpTestSuite()` as `SetupTestSuite()` and wonder why it's never called. - -## I have several test suites 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 suites 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 @@ -504,14 +419,14 @@ TEST_F(BarTest, Abc) { ... } TEST_F(BarTest, Def) { ... } ``` -## googletest 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 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 +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 `LOG` messages go to stderr, we decided to let googletest output go to +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: @@ -584,7 +499,7 @@ TEST(MyDeathTest, CompoundStatement) { ## I have a fixture class `FooTest`, but `TEST_F(FooTest, Bar)` gives me error ``"no matching function for call to `FooTest::FooTest()'"``. Why? -Googletest needs to be able to create objects of your test fixture class, so it +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: @@ -609,11 +524,11 @@ 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 googletest require the entire test suite, instead of individual tests, to be named *DeathTest when it uses ASSERT_DEATH? +## Why does GoogleTest require the entire test suite, instead of individual tests, to be named `*DeathTest` when it uses `ASSERT_DEATH`? -googletest does not interleave tests from different test suites. That is, it +GoogleTest does not interleave tests from different test suites. That is, it runs all tests in one test suite first, and then runs all tests in the next test -suite, and so on. googletest does this because it needs to set up a test suite +suite, and so on. GoogleTest does this because it needs to set up a test suite before the first test in it is run, and tear it down afterwards. Splitting up the test case would require multiple set-up and tear-down processes, which is inefficient and makes the semantics unclean. @@ -634,7 +549,7 @@ interleave tests from different test suites, 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 suite \*DeathTest when it contains both death tests and non-death tests. What do I do? +## But I don't like calling my entire test suite `*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 suite into `FooTest` and `FooDeathTest`, where the names make it clear that they are @@ -652,11 +567,11 @@ TEST_F(FooDeathTest, Uvw) { ... EXPECT_DEATH(...) ... } TEST_F(FooDeathTest, Xyz) { ... ASSERT_DEATH(...) ... } ``` -## 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? +## 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. +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 @@ -671,11 +586,11 @@ 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. See -[Tip of the Week #49](http://abseil.io/tips/49) for details. +[Tip of the Week #49](https://abseil.io/tips/49) for details. ## How do I suppress the memory leak messages on Windows? -Since the statically initialized googletest 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 @@ -689,13 +604,13 @@ 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. +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](http://en.wikipedia.org/wiki/Dependency_injection). You can inject +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`](http://docs.bazel.build/versions/master/be/common-definitions.html#common.testonly) attribute for BUILD targets helps to ensure +[`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 @@ -718,7 +633,7 @@ the `--gtest_also_run_disabled_tests` flag. Yes. The rule is **all test methods in the same test suite must use the same fixture -class.** This means that the following is **allowed** because both tests use the +class**. This means that the following is **allowed** because both tests use the same fixture class (`::testing::Test`). ```c++ @@ -736,7 +651,7 @@ TEST(CoolTest, DoSomething) { ``` However, the following code is **not allowed** and will produce a runtime error -from googletest because the test methods are using different test fixture +from GoogleTest because the test methods are using different test fixture classes with the same test suite name. ```c++ |