3 ## Why should test suite names and test names not contain underscore?
6 Note: Googletest reserves underscore (`_`) for special purpose keywords, such as
7 [the `DISABLED_` prefix](advanced.md#temporarily-disabling-tests), in addition
8 to the following rationale.
10 Underscore (`_`) is special, as C++ reserves the following to be used by the
11 compiler and the standard library:
13 1. any identifier that starts with an `_` followed by an upper-case letter, and
14 2. any identifier that contains two consecutive underscores (i.e. `__`)
15 *anywhere* in its name.
17 User code is *prohibited* from using such identifiers.
19 Now let's look at what this means for `TEST` and `TEST_F`.
21 Currently `TEST(TestSuiteName, TestName)` generates a class named
22 `TestSuiteName_TestName_Test`. What happens if `TestSuiteName` or `TestName`
25 1. If `TestSuiteName` starts with an `_` followed by an upper-case letter (say,
26 `_Foo`), we end up with `_Foo_TestName_Test`, which is reserved and thus
28 2. If `TestSuiteName` ends with an `_` (say, `Foo_`), we get
29 `Foo__TestName_Test`, which is invalid.
30 3. If `TestName` starts with an `_` (say, `_Bar`), we get
31 `TestSuiteName__Bar_Test`, which is invalid.
32 4. If `TestName` ends with an `_` (say, `Bar_`), we get
33 `TestSuiteName_Bar__Test`, which is invalid.
35 So clearly `TestSuiteName` and `TestName` cannot start or end with `_`
36 (Actually, `TestSuiteName` can start with `_` -- as long as the `_` isn't
37 followed by an upper-case letter. But that's getting complicated. So for
38 simplicity we just say that it cannot start with `_`.).
40 It may seem fine for `TestSuiteName` and `TestName` to contain `_` in the
41 middle. However, consider this:
44 TEST(Time, Flies_Like_An_Arrow) { ... }
45 TEST(Time_Flies, Like_An_Arrow) { ... }
48 Now, the two `TEST`s will both generate the same class
49 (`Time_Flies_Like_An_Arrow_Test`). That's not good.
51 So for simplicity, we just ask the users to avoid `_` in `TestSuiteName` and
52 `TestName`. The rule is more constraining than necessary, but it's simple and
53 easy to remember. It also gives googletest some wiggle room in case its
54 implementation needs to change in the future.
56 If you violate the rule, there may not be immediate consequences, but your test
57 may (just may) break with a new compiler (or a new version of the compiler you
58 are using) or with a new version of googletest. Therefore it's best to follow
61 ## Why does googletest support `EXPECT_EQ(NULL, ptr)` and `ASSERT_EQ(NULL, ptr)` but not `EXPECT_NE(NULL, ptr)` and `ASSERT_NE(NULL, ptr)`?
63 First of all, you can use `nullptr` with each of these macros, e.g.
64 `EXPECT_EQ(ptr, nullptr)`, `EXPECT_NE(ptr, nullptr)`, `ASSERT_EQ(ptr, nullptr)`,
65 `ASSERT_NE(ptr, nullptr)`. This is the preferred syntax in the style guide
66 because `nullptr` does not have the type problems that `NULL` does.
68 Due to some peculiarity of C++, it requires some non-trivial template meta
69 programming tricks to support using `NULL` as an argument of the `EXPECT_XX()`
70 and `ASSERT_XX()` macros. Therefore we only do it where it's most needed
71 (otherwise we make the implementation of googletest harder to maintain and more
72 error-prone than necessary).
74 Historically, the `EXPECT_EQ()` macro took the *expected* value as its first
75 argument and the *actual* value as the second, though this argument order is now
76 discouraged. It was reasonable that someone wanted
77 to write `EXPECT_EQ(NULL, some_expression)`, and this indeed was requested
78 several times. Therefore we implemented it.
80 The need for `EXPECT_NE(NULL, ptr)` wasn't nearly as strong. When the assertion
81 fails, you already know that `ptr` must be `NULL`, so it doesn't add any
82 information to print `ptr` in this case. That means `EXPECT_TRUE(ptr != NULL)`
85 If we were to support `EXPECT_NE(NULL, ptr)`, for consistency we'd have to
86 support `EXPECT_NE(ptr, NULL)` as well. This means using the template meta
87 programming tricks twice in the implementation, making it even harder to
88 understand and maintain. We believe the benefit doesn't justify the cost.
90 Finally, with the growth of the gMock matcher library, we are encouraging people
91 to use the unified `EXPECT_THAT(value, matcher)` syntax more often in tests. One
92 significant advantage of the matcher approach is that matchers can be easily
93 combined to form new matchers, while the `EXPECT_NE`, etc, macros cannot be
94 easily combined. Therefore we want to invest more in the matchers than in the
97 ## I need to test that different implementations of an interface satisfy some common requirements. Should I use typed tests or value-parameterized tests?
99 For testing various implementations of the same interface, either typed tests or
100 value-parameterized tests can get it done. It's really up to you the user to
101 decide which is more convenient for you, depending on your particular case. Some
104 * Typed tests can be easier to write if instances of the different
105 implementations can be created the same way, modulo the type. For example,
106 if all these implementations have a public default constructor (such that
107 you can write `new TypeParam`), or if their factory functions have the same
108 form (e.g. `CreateInstance<TypeParam>()`).
109 * Value-parameterized tests can be easier to write if you need different code
110 patterns to create different implementations' instances, e.g. `new Foo` vs
111 `new Bar(5)`. To accommodate for the differences, you can write factory
112 function wrappers and pass these function pointers to the tests as their
114 * When a typed test fails, the default output includes the name of the type,
115 which can help you quickly identify which implementation is wrong.
116 Value-parameterized tests only show the number of the failed iteration by
117 default. You will need to define a function that returns the iteration name
118 and pass it as the third parameter to INSTANTIATE_TEST_SUITE_P to have more
120 * When using typed tests, you need to make sure you are testing against the
121 interface type, not the concrete types (in other words, you want to make
122 sure `implicit_cast<MyInterface*>(my_concrete_impl)` works, not just that
123 `my_concrete_impl` works). It's less likely to make mistakes in this area
124 when using value-parameterized tests.
126 I hope I didn't confuse you more. :-) If you don't mind, I'd suggest you to give
127 both approaches a try. Practice is a much better way to grasp the subtle
128 differences between the two tools. Once you have some concrete experience, you
129 can much more easily decide which one to use the next time.
131 ## I got some run-time errors about invalid proto descriptors when using `ProtocolMessageEquals`. Help!
134 **Note:** `ProtocolMessageEquals` and `ProtocolMessageEquiv` are *deprecated*
135 now. Please use `EqualsProto`, etc instead.
137 `ProtocolMessageEquals` and `ProtocolMessageEquiv` were redefined recently and
138 are now less tolerant of invalid protocol buffer definitions. In particular, if
139 you have a `foo.proto` that doesn't fully qualify the type of a protocol message
140 it references (e.g. `message<Bar>` where it should be `message<blah.Bar>`), you
141 will now get run-time errors like:
144 ... descriptor.cc:...] Invalid proto descriptor for file "path/to/foo.proto":
145 ... descriptor.cc:...] blah.MyMessage.my_field: ".Bar" is not defined.
148 If you see this, your `.proto` file is broken and needs to be fixed by making
149 the types fully qualified. The new definition of `ProtocolMessageEquals` and
150 `ProtocolMessageEquiv` just happen to reveal your bug.
152 ## My death test modifies some state, but the change seems lost after the death test finishes. Why?
154 Death tests (`EXPECT_DEATH`, etc) are executed in a sub-process s.t. the
155 expected crash won't kill the test program (i.e. the parent process). As a
156 result, any in-memory side effects they incur are observable in their respective
157 sub-processes, but not in the parent process. You can think of them as running
158 in a parallel universe, more or less.
160 In particular, if you use mocking and the death test statement invokes some mock
161 methods, the parent process will think the calls have never occurred. Therefore,
162 you may want to move your `EXPECT_CALL` statements inside the `EXPECT_DEATH`
165 ## EXPECT_EQ(htonl(blah), blah_blah) generates weird compiler errors in opt mode. Is this a googletest bug?
167 Actually, the bug is in `htonl()`.
169 According to `'man htonl'`, `htonl()` is a *function*, which means it's valid to
170 use `htonl` as a function pointer. However, in opt mode `htonl()` is defined as
171 a *macro*, which breaks this usage.
173 Worse, the macro definition of `htonl()` uses a `gcc` extension and is *not*
174 standard C++. That hacky implementation has some ad hoc limitations. In
175 particular, it prevents you from writing `Foo<sizeof(htonl(x))>()`, where `Foo`
176 is a template that has an integral argument.
178 The implementation of `EXPECT_EQ(a, b)` uses `sizeof(... a ...)` inside a
179 template argument, and thus doesn't compile in opt mode when `a` contains a call
180 to `htonl()`. It is difficult to make `EXPECT_EQ` bypass the `htonl()` bug, as
181 the solution must work with different compilers on various platforms.
183 ## The compiler complains about "undefined references" to some static const member variables, but I did define them in the class body. What's wrong?
185 If your class has a static data member:
191 static const int kBar = 100;
195 You also need to define it *outside* of the class body in `foo.cc`:
198 const int Foo::kBar; // No initializer here.
201 Otherwise your code is **invalid C++**, and may break in unexpected ways. In
202 particular, using it in googletest comparison assertions (`EXPECT_EQ`, etc) will
203 generate an "undefined reference" linker error. The fact that "it used to work"
204 doesn't mean it's valid. It just means that you were lucky. :-)
206 If the declaration of the static data member is `constexpr` then it is
207 implicitly an `inline` definition, and a separate definition in `foo.cc` is not
214 static constexpr int kBar = 100; // Defines kBar, no need to do it in foo.cc.
218 ## Can I derive a test fixture from another?
222 Each test fixture has a corresponding and same named test suite. This means only
223 one test suite can use a particular fixture. Sometimes, however, multiple test
224 cases may want to use the same or slightly different fixtures. For example, you
225 may want to make sure that all of a GUI library's test suites don't leak
226 important system resources like fonts and brushes.
228 In googletest, you share a fixture among test suites by putting the shared logic
229 in a base test fixture, then deriving from that base a separate fixture for each
230 test suite that wants to use this common logic. You then use `TEST_F()` to write
231 tests using each derived fixture.
233 Typically, your code looks like this:
236 // Defines a base test fixture.
237 class BaseTest : public ::testing::Test {
242 // Derives a fixture FooTest from BaseTest.
243 class FooTest : public BaseTest {
245 void SetUp() override {
246 BaseTest::SetUp(); // Sets up the base fixture first.
247 ... additional set-up work ...
250 void TearDown() override {
251 ... clean-up work for FooTest ...
252 BaseTest::TearDown(); // Remember to tear down the base fixture
253 // after cleaning up FooTest!
256 ... functions and variables for FooTest ...
259 // Tests that use the fixture FooTest.
260 TEST_F(FooTest, Bar) { ... }
261 TEST_F(FooTest, Baz) { ... }
263 ... additional fixtures derived from BaseTest ...
266 If necessary, you can continue to derive test fixtures from a derived fixture.
267 googletest has no limit on how deep the hierarchy can be.
269 For a complete example using derived test fixtures, see
270 [sample5_unittest.cc](https://github.com/google/googletest/blob/master/googletest/samples/sample5_unittest.cc).
272 ## My compiler complains "void value not ignored as it ought to be." What does this mean?
274 You're probably using an `ASSERT_*()` in a function that doesn't return `void`.
275 `ASSERT_*()` can only be used in `void` functions, due to exceptions being
276 disabled by our build system. Please see more details
277 [here](advanced.md#assertion-placement).
279 ## My death test hangs (or seg-faults). How do I fix it?
281 In googletest, death tests are run in a child process and the way they work is
282 delicate. To write death tests you really need to understand how they work—see
283 the details at [Death Assertions](reference/assertions.md#death) in the
284 Assertions Reference.
286 In particular, death tests don't like having multiple threads in the parent
287 process. So the first thing you can try is to eliminate creating threads outside
288 of `EXPECT_DEATH()`. For example, you may want to use mocks or fake objects
289 instead of real ones in your tests.
291 Sometimes this is impossible as some library you must use may be creating
292 threads before `main()` is even reached. In this case, you can try to minimize
293 the chance of conflicts by either moving as many activities as possible inside
294 `EXPECT_DEATH()` (in the extreme case, you want to move everything inside), or
295 leaving as few things as possible in it. Also, you can try to set the death test
296 style to `"threadsafe"`, which is safer but slower, and see if it helps.
298 If you go with thread-safe death tests, remember that they rerun the test
299 program from the beginning in the child process. Therefore make sure your
300 program can run side-by-side with itself and is deterministic.
302 In the end, this boils down to good concurrent programming. You have to make
303 sure that there are no race conditions or deadlocks in your program. No silver
306 ## Should I use the constructor/destructor of the test fixture or SetUp()/TearDown()? {#CtorVsSetUp}
308 The first thing to remember is that googletest does **not** reuse the same test
309 fixture object across multiple tests. For each `TEST_F`, googletest will create
310 a **fresh** test fixture object, immediately call `SetUp()`, run the test body,
311 call `TearDown()`, and then delete the test fixture object.
313 When you need to write per-test set-up and tear-down logic, you have the choice
314 between using the test fixture constructor/destructor or `SetUp()/TearDown()`.
315 The former is usually preferred, as it has the following benefits:
317 * By initializing a member variable in the constructor, we have the option to
318 make it `const`, which helps prevent accidental changes to its value and
319 makes the tests more obviously correct.
320 * In case we need to subclass the test fixture class, the subclass'
321 constructor is guaranteed to call the base class' constructor *first*, and
322 the subclass' destructor is guaranteed to call the base class' destructor
323 *afterward*. With `SetUp()/TearDown()`, a subclass may make the mistake of
324 forgetting to call the base class' `SetUp()/TearDown()` or call them at the
327 You may still want to use `SetUp()/TearDown()` in the following cases:
329 * C++ does not allow virtual function calls in constructors and destructors.
330 You can call a method declared as virtual, but it will not use dynamic
331 dispatch, it will use the definition from the class the constructor of which
332 is currently executing. This is because calling a virtual method before the
333 derived class constructor has a chance to run is very dangerous - the
334 virtual method might operate on uninitialized data. Therefore, if you need
335 to call a method that will be overridden in a derived class, you have to use
336 `SetUp()/TearDown()`.
337 * In the body of a constructor (or destructor), it's not possible to use the
338 `ASSERT_xx` macros. Therefore, if the set-up operation could cause a fatal
339 test failure that should prevent the test from running, it's necessary to
340 use `abort` and abort the whole test
341 executable, or to use `SetUp()` instead of a constructor.
342 * If the tear-down operation could throw an exception, you must use
343 `TearDown()` as opposed to the destructor, as throwing in a destructor leads
344 to undefined behavior and usually will kill your program right away. Note
345 that many standard libraries (like STL) may throw when exceptions are
346 enabled in the compiler. Therefore you should prefer `TearDown()` if you
347 want to write portable tests that work with or without exceptions.
348 * The googletest team is considering making the assertion macros throw on
349 platforms where exceptions are enabled (e.g. Windows, Mac OS, and Linux
350 client-side), which will eliminate the need for the user to propagate
351 failures from a subroutine to its caller. Therefore, you shouldn't use
352 googletest assertions in a destructor if your code could run on such a
355 ## The compiler complains "no matching function to call" when I use ASSERT_PRED*. How do I fix it?
357 See details for [`EXPECT_PRED*`](reference/assertions.md#EXPECT_PRED) in the
358 Assertions Reference.
360 ## My compiler complains about "ignoring return value" when I call RUN_ALL_TESTS(). Why?
362 Some people had been ignoring the return value of `RUN_ALL_TESTS()`. That is,
366 return RUN_ALL_TESTS();
375 This is **wrong and dangerous**. The testing services needs to see the return
376 value of `RUN_ALL_TESTS()` in order to determine if a test has passed. If your
377 `main()` function ignores it, your test will be considered successful even if it
378 has a googletest assertion failure. Very bad.
380 We have decided to fix this (thanks to Michael Chastain for the idea). Now, your
381 code will no longer be able to ignore `RUN_ALL_TESTS()` when compiled with
382 `gcc`. If you do so, you'll get a compiler error.
384 If you see the compiler complaining about you ignoring the return value of
385 `RUN_ALL_TESTS()`, the fix is simple: just make sure its value is used as the
386 return value of `main()`.
388 But how could we introduce a change that breaks existing tests? Well, in this
389 case, the code was already broken in the first place, so we didn't break it. :-)
391 ## My compiler complains that a constructor (or destructor) cannot return a value. What's going on?
393 Due to a peculiarity of C++, in order to support the syntax for streaming
394 messages to an `ASSERT_*`, e.g.
397 ASSERT_EQ(1, Foo()) << "blah blah" << foo;
400 we had to give up using `ASSERT*` and `FAIL*` (but not `EXPECT*` and
401 `ADD_FAILURE*`) in constructors and destructors. The workaround is to move the
402 content of your constructor/destructor to a private void member function, or
403 switch to `EXPECT_*()` if that works. This
404 [section](advanced.md#assertion-placement) in the user's guide explains it.
406 ## My SetUp() function is not called. Why?
408 C++ is case-sensitive. Did you spell it as `Setup()`?
410 Similarly, sometimes people spell `SetUpTestSuite()` as `SetupTestSuite()` and
411 wonder why it's never called.
414 ## 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.
416 You don't have to. Instead of
419 class FooTest : public BaseTest {};
421 TEST_F(FooTest, Abc) { ... }
422 TEST_F(FooTest, Def) { ... }
424 class BarTest : public BaseTest {};
426 TEST_F(BarTest, Abc) { ... }
427 TEST_F(BarTest, Def) { ... }
430 you can simply `typedef` the test fixtures:
433 typedef BaseTest FooTest;
435 TEST_F(FooTest, Abc) { ... }
436 TEST_F(FooTest, Def) { ... }
438 typedef BaseTest BarTest;
440 TEST_F(BarTest, Abc) { ... }
441 TEST_F(BarTest, Def) { ... }
444 ## googletest output is buried in a whole bunch of LOG messages. What do I do?
446 The googletest output is meant to be a concise and human-friendly report. If
447 your test generates textual output itself, it will mix with the googletest
448 output, making it hard to read. However, there is an easy solution to this
451 Since `LOG` messages go to stderr, we decided to let googletest output go to
452 stdout. This way, you can easily separate the two using redirection. For
456 $ ./my_test > gtest_output.txt
459 ## Why should I prefer test fixtures over global variables?
461 There are several good reasons:
463 1. It's likely your test needs to change the states of its global variables.
464 This makes it difficult to keep side effects from escaping one test and
465 contaminating others, making debugging difficult. By using fixtures, each
466 test has a fresh set of variables that's different (but with the same
467 names). Thus, tests are kept independent of each other.
468 2. Global variables pollute the global namespace.
469 3. Test fixtures can be reused via subclassing, which cannot be done easily
470 with global variables. This is useful if many test suites have something in
473 ## What can the statement argument in ASSERT_DEATH() be?
475 `ASSERT_DEATH(statement, matcher)` (or any death assertion macro) can be used
476 wherever *`statement`* is valid. So basically *`statement`* can be any C++
477 statement that makes sense in the current context. In particular, it can
478 reference global and/or local variables, and can be:
480 * a simple function call (often the case),
481 * a complex expression, or
482 * a compound statement.
484 Some examples are shown here:
487 // A death test can be a simple function call.
488 TEST(MyDeathTest, FunctionCall) {
489 ASSERT_DEATH(Xyz(5), "Xyz failed");
492 // Or a complex expression that references variables and functions.
493 TEST(MyDeathTest, ComplexExpression) {
494 const bool c = Condition();
495 ASSERT_DEATH((c ? Func1(0) : object2.Method("test")),
496 "(Func1|Method) failed");
499 // Death assertions can be used anywhere in a function. In
500 // particular, they can be inside a loop.
501 TEST(MyDeathTest, InsideLoop) {
502 // Verifies that Foo(0), Foo(1), ..., and Foo(4) all die.
503 for (int i = 0; i < 5; i++) {
504 EXPECT_DEATH_M(Foo(i), "Foo has \\d+ errors",
505 ::testing::Message() << "where i is " << i);
509 // A death assertion can contain a compound statement.
510 TEST(MyDeathTest, CompoundStatement) {
511 // Verifies that at lease one of Bar(0), Bar(1), ..., and
514 for (int i = 0; i < 5; i++) {
518 "Bar has \\d+ errors");
522 ## I have a fixture class `FooTest`, but `TEST_F(FooTest, Bar)` gives me error ``"no matching function for call to `FooTest::FooTest()'"``. Why?
524 Googletest needs to be able to create objects of your test fixture class, so it
525 must have a default constructor. Normally the compiler will define one for you.
526 However, there are cases where you have to define your own:
528 * If you explicitly declare a non-default constructor for class `FooTest`
529 (`DISALLOW_EVIL_CONSTRUCTORS()` does this), then you need to define a
530 default constructor, even if it would be empty.
531 * If `FooTest` has a const non-static data member, then you have to define the
532 default constructor *and* initialize the const member in the initializer
533 list of the constructor. (Early versions of `gcc` doesn't force you to
534 initialize the const member. It's a bug that has been fixed in `gcc 4`.)
536 ## Why does ASSERT_DEATH complain about previous threads that were already joined?
538 With the Linux pthread library, there is no turning back once you cross the line
539 from a single thread to multiple threads. The first time you create a thread, a
540 manager thread is created in addition, so you get 3, not 2, threads. Later when
541 the thread you create joins the main thread, the thread count decrements by 1,
542 but the manager thread will never be killed, so you still have 2 threads, which
543 means you cannot safely run a death test.
545 The new NPTL thread library doesn't suffer from this problem, as it doesn't
546 create a manager thread. However, if you don't control which machine your test
547 runs on, you shouldn't depend on this.
549 ## Why does googletest require the entire test suite, instead of individual tests, to be named *DeathTest when it uses ASSERT_DEATH?
551 googletest does not interleave tests from different test suites. That is, it
552 runs all tests in one test suite first, and then runs all tests in the next test
553 suite, and so on. googletest does this because it needs to set up a test suite
554 before the first test in it is run, and tear it down afterwards. Splitting up
555 the test case would require multiple set-up and tear-down processes, which is
556 inefficient and makes the semantics unclean.
558 If we were to determine the order of tests based on test name instead of test
559 case name, then we would have a problem with the following situation:
562 TEST_F(FooTest, AbcDeathTest) { ... }
563 TEST_F(FooTest, Uvw) { ... }
565 TEST_F(BarTest, DefDeathTest) { ... }
566 TEST_F(BarTest, Xyz) { ... }
569 Since `FooTest.AbcDeathTest` needs to run before `BarTest.Xyz`, and we don't
570 interleave tests from different test suites, we need to run all tests in the
571 `FooTest` case before running any test in the `BarTest` case. This contradicts
572 with the requirement to run `BarTest.DefDeathTest` before `FooTest.Uvw`.
574 ## 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?
576 You don't have to, but if you like, you may split up the test suite into
577 `FooTest` and `FooDeathTest`, where the names make it clear that they are
581 class FooTest : public ::testing::Test { ... };
583 TEST_F(FooTest, Abc) { ... }
584 TEST_F(FooTest, Def) { ... }
586 using FooDeathTest = FooTest;
588 TEST_F(FooDeathTest, Uvw) { ... EXPECT_DEATH(...) ... }
589 TEST_F(FooDeathTest, Xyz) { ... ASSERT_DEATH(...) ... }
592 ## 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?
594 Printing the LOG messages generated by the statement inside `EXPECT_DEATH()`
595 makes it harder to search for real problems in the parent's log. Therefore,
596 googletest only prints them when the death test has failed.
598 If you really need to see such LOG messages, a workaround is to temporarily
599 break the death test (e.g. by changing the regex pattern it is expected to
600 match). Admittedly, this is a hack. We'll consider a more permanent solution
601 after the fork-and-exec-style death tests are implemented.
603 ## The compiler complains about `no match for 'operator<<'` when I use an assertion. What gives?
605 If you use a user-defined type `FooType` in an assertion, you must make sure
606 there is an `std::ostream& operator<<(std::ostream&, const FooType&)` function
607 defined such that we can print a value of `FooType`.
609 In addition, if `FooType` is declared in a name space, the `<<` operator also
610 needs to be defined in the *same* name space. See
611 [Tip of the Week #49](http://abseil.io/tips/49) for details.
613 ## How do I suppress the memory leak messages on Windows?
615 Since the statically initialized googletest singleton requires allocations on
616 the heap, the Visual C++ memory leak detector will report memory leaks at the
617 end of the program run. The easiest way to avoid this is to use the
618 `_CrtMemCheckpoint` and `_CrtMemDumpAllObjectsSince` calls to not report any
619 statically initialized heap objects. See MSDN for more details and additional
620 heap check/debug routines.
622 ## How can my code detect if it is running in a test?
624 If you write code that sniffs whether it's running in a test and does different
625 things accordingly, you are leaking test-only logic into production code and
626 there is no easy way to ensure that the test-only code paths aren't run by
627 mistake in production. Such cleverness also leads to
628 [Heisenbugs](https://en.wikipedia.org/wiki/Heisenbug). Therefore we strongly
629 advise against the practice, and googletest doesn't provide a way to do it.
631 In general, the recommended way to cause the code to behave differently under
632 test is [Dependency Injection](http://en.wikipedia.org/wiki/Dependency_injection). You can inject
633 different functionality from the test and from the production code. Since your
634 production code doesn't link in the for-test logic at all (the
635 [`testonly`](http://docs.bazel.build/versions/master/be/common-definitions.html#common.testonly) attribute for BUILD targets helps to ensure
636 that), there is no danger in accidentally running it.
638 However, if you *really*, *really*, *really* have no choice, and if you follow
639 the rule of ending your test program names with `_test`, you can use the
640 *horrible* hack of sniffing your executable name (`argv[0]` in `main()`) to know
641 whether the code is under test.
643 ## How do I temporarily disable a test?
645 If you have a broken test that you cannot fix right away, you can add the
646 `DISABLED_` prefix to its name. This will exclude it from execution. This is
647 better than commenting out the code or using `#if 0`, as disabled tests are
648 still compiled (and thus won't rot).
650 To include disabled tests in test execution, just invoke the test program with
651 the `--gtest_also_run_disabled_tests` flag.
653 ## Is it OK if I have two separate `TEST(Foo, Bar)` test methods defined in different namespaces?
657 The rule is **all test methods in the same test suite must use the same fixture
658 class.** This means that the following is **allowed** because both tests use the
659 same fixture class (`::testing::Test`).
663 TEST(CoolTest, DoSomething) {
669 TEST(CoolTest, DoSomething) {
675 However, the following code is **not allowed** and will produce a runtime error
676 from googletest because the test methods are using different test fixture
677 classes with the same test suite name.
681 class CoolTest : public ::testing::Test {}; // Fixture foo::CoolTest
682 TEST_F(CoolTest, DoSomething) {
688 class CoolTest : public ::testing::Test {}; // Fixture: bar::CoolTest
689 TEST_F(CoolTest, DoSomething) {