1 # gMock for Dummies {#GMockForDummies}
3 <!-- GOOGLETEST_CM0013 DO NOT DELETE -->
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9 When you write a prototype or test, often it's not feasible or wise to rely on
10 real objects entirely. A **mock object** implements the same interface as a real
11 object (so it can be used as one), but lets you specify at run time how it will
12 be used and what it should do (which methods will be called? in which order? how
13 many times? with what arguments? what will they return? etc).
15 **Note:** It is easy to confuse the term *fake objects* with mock objects. Fakes
16 and mocks actually mean very different things in the Test-Driven Development
19 * **Fake** objects have working implementations, but usually take some
20 shortcut (perhaps to make the operations less expensive), which makes them
21 not suitable for production. An in-memory file system would be an example of
23 * **Mocks** are objects pre-programmed with *expectations*, which form a
24 specification of the calls they are expected to receive.
26 If all this seems too abstract for you, don't worry - the most important thing
27 to remember is that a mock allows you to check the *interaction* between itself
28 and code that uses it. The difference between fakes and mocks shall become much
29 clearer once you start to use mocks.
31 **gMock** is a library (sometimes we also call it a "framework" to make it sound
32 cool) for creating mock classes and using them. It does to C++ what
33 jMock/EasyMock does to Java (well, more or less).
37 1. first, you use some simple macros to describe the interface you want to
38 mock, and they will expand to the implementation of your mock class;
39 2. next, you create some mock objects and specify its expectations and behavior
40 using an intuitive syntax;
41 3. then you exercise code that uses the mock objects. gMock will catch any
42 violation to the expectations as soon as it arises.
46 While mock objects help you remove unnecessary dependencies in tests and make
47 them fast and reliable, using mocks manually in C++ is *hard*:
49 * Someone has to implement the mocks. The job is usually tedious and
50 error-prone. No wonder people go great distance to avoid it.
51 * The quality of those manually written mocks is a bit, uh, unpredictable. You
52 may see some really polished ones, but you may also see some that were
53 hacked up in a hurry and have all sorts of ad hoc restrictions.
54 * The knowledge you gained from using one mock doesn't transfer to the next
57 In contrast, Java and Python programmers have some fine mock frameworks (jMock,
58 EasyMock, [Mox](http://wtf/mox), etc), which automate the creation of mocks. As
59 a result, mocking is a proven effective technique and widely adopted practice in
60 those communities. Having the right tool absolutely makes the difference.
62 gMock was built to help C++ programmers. It was inspired by jMock and EasyMock,
63 but designed with C++'s specifics in mind. It is your friend if any of the
64 following problems is bothering you:
66 * You are stuck with a sub-optimal design and wish you had done more
67 prototyping before it was too late, but prototyping in C++ is by no means
69 * Your tests are slow as they depend on too many libraries or use expensive
70 resources (e.g. a database).
71 * Your tests are brittle as some resources they use are unreliable (e.g. the
73 * You want to test how your code handles a failure (e.g. a file checksum
74 error), but it's not easy to cause one.
75 * You need to make sure that your module interacts with other modules in the
76 right way, but it's hard to observe the interaction; therefore you resort to
77 observing the side effects at the end of the action, but it's awkward at
79 * You want to "mock out" your dependencies, except that they don't have mock
80 implementations yet; and, frankly, you aren't thrilled by some of those
83 We encourage you to use gMock as
85 * a *design* tool, for it lets you experiment with your interface design early
86 and often. More iterations lead to better designs!
87 * a *testing* tool to cut your tests' outbound dependencies and probe the
88 interaction between your module and its collaborators.
92 gMock is bundled with googletest.
94 ## A Case for Mock Turtles
96 Let's look at an example. Suppose you are developing a graphics program that
97 relies on a [LOGO](http://en.wikipedia.org/wiki/Logo_programming_language)-like
98 API for drawing. How would you test that it does the right thing? Well, you can
99 run it and compare the screen with a golden screen snapshot, but let's admit it:
100 tests like this are expensive to run and fragile (What if you just upgraded to a
101 shiny new graphics card that has better anti-aliasing? Suddenly you have to
102 update all your golden images.). It would be too painful if all your tests are
103 like this. Fortunately, you learned about
104 [Dependency Injection](http://en.wikipedia.org/wiki/Dependency_injection) and know the right thing
105 to do: instead of having your application talk to the system API directly, wrap
106 the API in an interface (say, `Turtle`) and code to that interface:
112 virtual void PenUp() = 0;
113 virtual void PenDown() = 0;
114 virtual void Forward(int distance) = 0;
115 virtual void Turn(int degrees) = 0;
116 virtual void GoTo(int x, int y) = 0;
117 virtual int GetX() const = 0;
118 virtual int GetY() const = 0;
122 (Note that the destructor of `Turtle` **must** be virtual, as is the case for
123 **all** classes you intend to inherit from - otherwise the destructor of the
124 derived class will not be called when you delete an object through a base
125 pointer, and you'll get corrupted program states like memory leaks.)
127 You can control whether the turtle's movement will leave a trace using `PenUp()`
128 and `PenDown()`, and control its movement using `Forward()`, `Turn()`, and
129 `GoTo()`. Finally, `GetX()` and `GetY()` tell you the current position of the
132 Your program will normally use a real implementation of this interface. In
133 tests, you can use a mock implementation instead. This allows you to easily
134 check what drawing primitives your program is calling, with what arguments, and
135 in which order. Tests written this way are much more robust (they won't break
136 because your new machine does anti-aliasing differently), easier to read and
137 maintain (the intent of a test is expressed in the code, not in some binary
138 images), and run *much, much faster*.
140 ## Writing the Mock Class
142 If you are lucky, the mocks you need to use have already been implemented by
143 some nice people. If, however, you find yourself in the position to write a mock
144 class, relax - gMock turns this task into a fun game! (Well, almost.)
148 Using the `Turtle` interface as example, here are the simple steps you need to
151 * Derive a class `MockTurtle` from `Turtle`.
152 * Take a *virtual* function of `Turtle` (while it's possible to
153 [mock non-virtual methods using templates](cook_book.md#MockingNonVirtualMethods),
154 it's much more involved).
155 * In the `public:` section of the child class, write `MOCK_METHOD();`
156 * Now comes the fun part: you take the function signature, cut-and-paste it
157 into the macro, and add two commas - one between the return type and the
158 name, another between the name and the argument list.
159 * If you're mocking a const method, add a 4th parameter containing `(const)`
160 (the parentheses are required).
161 * Since you're overriding a virtual method, we suggest adding the `override`
162 keyword. For const methods the 4th parameter becomes `(const, override)`,
163 for non-const methods just `(override)`. This isn't mandatory.
164 * Repeat until all virtual functions you want to mock are done. (It goes
165 without saying that *all* pure virtual methods in your abstract class must
166 be either mocked or overridden.)
168 After the process, you should have something like:
171 #include "gmock/gmock.h" // Brings in gMock.
173 class MockTurtle : public Turtle {
176 MOCK_METHOD(void, PenUp, (), (override));
177 MOCK_METHOD(void, PenDown, (), (override));
178 MOCK_METHOD(void, Forward, (int distance), (override));
179 MOCK_METHOD(void, Turn, (int degrees), (override));
180 MOCK_METHOD(void, GoTo, (int x, int y), (override));
181 MOCK_METHOD(int, GetX, (), (const, override));
182 MOCK_METHOD(int, GetY, (), (const, override));
186 You don't need to define these mock methods somewhere else - the `MOCK_METHOD`
187 macro will generate the definitions for you. It's that simple!
191 When you define a mock class, you need to decide where to put its definition.
192 Some people put it in a `_test.cc`. This is fine when the interface being mocked
193 (say, `Foo`) is owned by the same person or team. Otherwise, when the owner of
194 `Foo` changes it, your test could break. (You can't really expect `Foo`'s
195 maintainer to fix every test that uses `Foo`, can you?)
197 So, the rule of thumb is: if you need to mock `Foo` and it's owned by others,
198 define the mock class in `Foo`'s package (better, in a `testing` sub-package
199 such that you can clearly separate production code and testing utilities), put
200 it in a `.h` and a `cc_library`. Then everyone can reference them from their
201 tests. If `Foo` ever changes, there is only one copy of `MockFoo` to change, and
202 only tests that depend on the changed methods need to be fixed.
204 Another way to do it: you can introduce a thin layer `FooAdaptor` on top of
205 `Foo` and code to this new interface. Since you own `FooAdaptor`, you can absorb
206 changes in `Foo` much more easily. While this is more work initially, carefully
207 choosing the adaptor interface can make your code easier to write and more
208 readable (a net win in the long run), as you can choose `FooAdaptor` to fit your
209 specific domain much better than `Foo` does.
211 <!-- GOOGLETEST_CM0029 DO NOT DELETE -->
213 ## Using Mocks in Tests
215 Once you have a mock class, using it is easy. The typical work flow is:
217 1. Import the gMock names from the `testing` namespace such that you can use
218 them unqualified (You only have to do it once per file). Remember that
219 namespaces are a good idea.
220 2. Create some mock objects.
221 3. Specify your expectations on them (How many times will a method be called?
222 With what arguments? What should it do? etc.).
223 4. Exercise some code that uses the mocks; optionally, check the result using
224 googletest assertions. If a mock method is called more than expected or with
225 wrong arguments, you'll get an error immediately.
226 5. When a mock is destructed, gMock will automatically check whether all
227 expectations on it have been satisfied.
232 #include "path/to/mock-turtle.h"
233 #include "gmock/gmock.h"
234 #include "gtest/gtest.h"
236 using ::testing::AtLeast; // #1
238 TEST(PainterTest, CanDrawSomething) {
239 MockTurtle turtle; // #2
240 EXPECT_CALL(turtle, PenDown()) // #3
243 Painter painter(&turtle); // #4
245 EXPECT_TRUE(painter.DrawCircle(0, 0, 10)); // #5
249 As you might have guessed, this test checks that `PenDown()` is called at least
250 once. If the `painter` object didn't call this method, your test will fail with
254 path/to/my_test.cc:119: Failure
255 Actual function call count doesn't match this expectation:
256 Actually: never called;
257 Expected: called at least once.
262 **Tip 1:** If you run the test from an Emacs buffer, you can hit `<Enter>` on
263 the line number to jump right to the failed expectation.
265 **Tip 2:** If your mock objects are never deleted, the final verification won't
266 happen. Therefore it's a good idea to turn on the heap checker in your tests
267 when you allocate mocks on the heap. You get that automatically if you use the
268 `gtest_main` library already.
270 **Important note:** gMock requires expectations to be set **before** the mock
271 functions are called, otherwise the behavior is **undefined**. In particular,
272 you mustn't interleave `EXPECT_CALL()s` and calls to the mock functions.
274 This means `EXPECT_CALL()` should be read as expecting that a call will occur
275 *in the future*, not that a call has occurred. Why does gMock work like that?
276 Well, specifying the expectation beforehand allows gMock to report a violation
277 as soon as it rises, when the context (stack trace, etc) is still available.
278 This makes debugging much easier.
280 Admittedly, this test is contrived and doesn't do much. You can easily achieve
281 the same effect without using gMock. However, as we shall reveal soon, gMock
282 allows you to do *so much more* with the mocks.
284 ## Setting Expectations
286 The key to using a mock object successfully is to set the *right expectations*
287 on it. If you set the expectations too strict, your test will fail as the result
288 of unrelated changes. If you set them too loose, bugs can slip through. You want
289 to do it just right such that your test can catch exactly the kind of bugs you
290 intend it to catch. gMock provides the necessary means for you to do it "just
295 In gMock we use the `EXPECT_CALL()` macro to set an expectation on a mock
296 method. The general syntax is:
299 EXPECT_CALL(mock_object, method(matchers))
302 .WillRepeatedly(action);
305 The macro has two arguments: first the mock object, and then the method and its
306 arguments. Note that the two are separated by a comma (`,`), not a period (`.`).
307 (Why using a comma? The answer is that it was necessary for technical reasons.)
308 If the method is not overloaded, the macro can also be called without matchers:
311 EXPECT_CALL(mock_object, non-overloaded-method)
314 .WillRepeatedly(action);
317 This syntax allows the test writer to specify "called with any arguments"
318 without explicitly specifying the number or types of arguments. To avoid
319 unintended ambiguity, this syntax may only be used for methods which are not
322 Either form of the macro can be followed by some optional *clauses* that provide
323 more information about the expectation. We'll discuss how each clause works in
326 This syntax is designed to make an expectation read like English. For example,
327 you can probably guess that
330 using ::testing::Return;
332 EXPECT_CALL(turtle, GetX())
334 .WillOnce(Return(100))
335 .WillOnce(Return(150))
336 .WillRepeatedly(Return(200));
339 says that the `turtle` object's `GetX()` method will be called five times, it
340 will return 100 the first time, 150 the second time, and then 200 every time.
341 Some people like to call this style of syntax a Domain-Specific Language (DSL).
343 **Note:** Why do we use a macro to do this? Well it serves two purposes: first
344 it makes expectations easily identifiable (either by `gsearch` or by a human
345 reader), and second it allows gMock to include the source file location of a
346 failed expectation in messages, making debugging easier.
348 ### Matchers: What Arguments Do We Expect?
350 When a mock function takes arguments, we may specify what arguments we are
351 expecting, for example:
354 // Expects the turtle to move forward by 100 units.
355 EXPECT_CALL(turtle, Forward(100));
358 Oftentimes you do not want to be too specific. Remember that talk about tests
359 being too rigid? Over specification leads to brittle tests and obscures the
360 intent of tests. Therefore we encourage you to specify only what's necessary—no
361 more, no less. If you aren't interested in the value of an argument, write `_`
362 as the argument, which means "anything goes":
367 // Expects that the turtle jumps to somewhere on the x=50 line.
368 EXPECT_CALL(turtle, GoTo(50, _));
371 `_` is an instance of what we call **matchers**. A matcher is like a predicate
372 and can test whether an argument is what we'd expect. You can use a matcher
373 inside `EXPECT_CALL()` wherever a function argument is expected. `_` is a
374 convenient way of saying "any value".
376 In the above examples, `100` and `50` are also matchers; implicitly, they are
377 the same as `Eq(100)` and `Eq(50)`, which specify that the argument must be
378 equal (using `operator==`) to the matcher argument. There are many
379 [built-in matchers](cheat_sheet.md#MatcherList) for common types (as well as
380 [custom matchers](cook_book.md#NewMatchers)); for example:
385 // Expects the turtle moves forward by at least 100.
386 EXPECT_CALL(turtle, Forward(Ge(100)));
389 If you don't care about *any* arguments, rather than specify `_` for each of
390 them you may instead omit the parameter list:
393 // Expects the turtle to move forward.
394 EXPECT_CALL(turtle, Forward);
395 // Expects the turtle to jump somewhere.
396 EXPECT_CALL(turtle, GoTo);
399 This works for all non-overloaded methods; if a method is overloaded, you need
400 to help gMock resolve which overload is expected by specifying the number of
401 arguments and possibly also the
402 [types of the arguments](cook_book.md#SelectOverload).
404 ### Cardinalities: How Many Times Will It Be Called?
406 The first clause we can specify following an `EXPECT_CALL()` is `Times()`. We
407 call its argument a **cardinality** as it tells *how many times* the call should
408 occur. It allows us to repeat an expectation many times without actually writing
409 it as many times. More importantly, a cardinality can be "fuzzy", just like a
410 matcher can be. This allows a user to express the intent of a test exactly.
412 An interesting special case is when we say `Times(0)`. You may have guessed - it
413 means that the function shouldn't be called with the given arguments at all, and
414 gMock will report a googletest failure whenever the function is (wrongfully)
417 We've seen `AtLeast(n)` as an example of fuzzy cardinalities earlier. For the
418 list of built-in cardinalities you can use, see
419 [here](cheat_sheet.md#CardinalityList).
421 The `Times()` clause can be omitted. **If you omit `Times()`, gMock will infer
422 the cardinality for you.** The rules are easy to remember:
424 * If **neither** `WillOnce()` **nor** `WillRepeatedly()` is in the
425 `EXPECT_CALL()`, the inferred cardinality is `Times(1)`.
426 * If there are *n* `WillOnce()`'s but **no** `WillRepeatedly()`, where *n* >=
427 1, the cardinality is `Times(n)`.
428 * If there are *n* `WillOnce()`'s and **one** `WillRepeatedly()`, where *n* >=
429 0, the cardinality is `Times(AtLeast(n))`.
431 **Quick quiz:** what do you think will happen if a function is expected to be
432 called twice but actually called four times?
434 ### Actions: What Should It Do?
436 Remember that a mock object doesn't really have a working implementation? We as
437 users have to tell it what to do when a method is invoked. This is easy in
440 First, if the return type of a mock function is a built-in type or a pointer,
441 the function has a **default action** (a `void` function will just return, a
442 `bool` function will return `false`, and other functions will return 0). In
443 addition, in C++ 11 and above, a mock function whose return type is
444 default-constructible (i.e. has a default constructor) has a default action of
445 returning a default-constructed value. If you don't say anything, this behavior
448 Second, if a mock function doesn't have a default action, or the default action
449 doesn't suit you, you can specify the action to be taken each time the
450 expectation matches using a series of `WillOnce()` clauses followed by an
451 optional `WillRepeatedly()`. For example,
454 using ::testing::Return;
456 EXPECT_CALL(turtle, GetX())
457 .WillOnce(Return(100))
458 .WillOnce(Return(200))
459 .WillOnce(Return(300));
462 says that `turtle.GetX()` will be called *exactly three times* (gMock inferred
463 this from how many `WillOnce()` clauses we've written, since we didn't
464 explicitly write `Times()`), and will return 100, 200, and 300 respectively.
467 using ::testing::Return;
469 EXPECT_CALL(turtle, GetY())
470 .WillOnce(Return(100))
471 .WillOnce(Return(200))
472 .WillRepeatedly(Return(300));
475 says that `turtle.GetY()` will be called *at least twice* (gMock knows this as
476 we've written two `WillOnce()` clauses and a `WillRepeatedly()` while having no
477 explicit `Times()`), will return 100 and 200 respectively the first two times,
478 and 300 from the third time on.
480 Of course, if you explicitly write a `Times()`, gMock will not try to infer the
481 cardinality itself. What if the number you specified is larger than there are
482 `WillOnce()` clauses? Well, after all `WillOnce()`s are used up, gMock will do
483 the *default* action for the function every time (unless, of course, you have a
484 `WillRepeatedly()`.).
486 What can we do inside `WillOnce()` besides `Return()`? You can return a
487 reference using `ReturnRef(*variable*)`, or invoke a pre-defined function, among
488 [others](cook_book.md#using-actions).
490 **Important note:** The `EXPECT_CALL()` statement evaluates the action clause
491 only once, even though the action may be performed many times. Therefore you
492 must be careful about side effects. The following may not do what you want:
495 using ::testing::Return;
498 EXPECT_CALL(turtle, GetX())
500 .WillRepeatedly(Return(n++));
503 Instead of returning 100, 101, 102, ..., consecutively, this mock function will
504 always return 100 as `n++` is only evaluated once. Similarly, `Return(new Foo)`
505 will create a new `Foo` object when the `EXPECT_CALL()` is executed, and will
506 return the same pointer every time. If you want the side effect to happen every
507 time, you need to define a custom action, which we'll teach in the
508 [cook book](http://<!-- GOOGLETEST_CM0012 DO NOT DELETE -->).
510 Time for another quiz! What do you think the following means?
513 using ::testing::Return;
515 EXPECT_CALL(turtle, GetY())
517 .WillOnce(Return(100));
520 Obviously `turtle.GetY()` is expected to be called four times. But if you think
521 it will return 100 every time, think twice! Remember that one `WillOnce()`
522 clause will be consumed each time the function is invoked and the default action
523 will be taken afterwards. So the right answer is that `turtle.GetY()` will
524 return 100 the first time, but **return 0 from the second time on**, as
525 returning 0 is the default action for `int` functions.
527 ### Using Multiple Expectations {#MultiExpectations}
529 So far we've only shown examples where you have a single expectation. More
530 realistically, you'll specify expectations on multiple mock methods which may be
531 from multiple mock objects.
533 By default, when a mock method is invoked, gMock will search the expectations in
534 the **reverse order** they are defined, and stop when an active expectation that
535 matches the arguments is found (you can think of it as "newer rules override
536 older ones."). If the matching expectation cannot take any more calls, you will
537 get an upper-bound-violated failure. Here's an example:
542 EXPECT_CALL(turtle, Forward(_)); // #1
543 EXPECT_CALL(turtle, Forward(10)) // #2
547 If `Forward(10)` is called three times in a row, the third time it will be an
548 error, as the last matching expectation (#2) has been saturated. If, however,
549 the third `Forward(10)` call is replaced by `Forward(20)`, then it would be OK,
550 as now #1 will be the matching expectation.
552 **Note:** Why does gMock search for a match in the *reverse* order of the
553 expectations? The reason is that this allows a user to set up the default
554 expectations in a mock object's constructor or the test fixture's set-up phase
555 and then customize the mock by writing more specific expectations in the test
556 body. So, if you have two expectations on the same method, you want to put the
557 one with more specific matchers **after** the other, or the more specific rule
558 would be shadowed by the more general one that comes after it.
560 **Tip:** It is very common to start with a catch-all expectation for a method
561 and `Times(AnyNumber())` (omitting arguments, or with `_` for all arguments, if
562 overloaded). This makes any calls to the method expected. This is not necessary
563 for methods that are not mentioned at all (these are "uninteresting"), but is
564 useful for methods that have some expectations, but for which other calls are
566 [Understanding Uninteresting vs Unexpected Calls](cook_book.md#uninteresting-vs-unexpected).
568 ### Ordered vs Unordered Calls {#OrderedCalls}
570 By default, an expectation can match a call even though an earlier expectation
571 hasn't been satisfied. In other words, the calls don't have to occur in the
572 order the expectations are specified.
574 Sometimes, you may want all the expected calls to occur in a strict order. To
575 say this in gMock is easy:
578 using ::testing::InSequence;
580 TEST(FooTest, DrawsLineSegment) {
585 EXPECT_CALL(turtle, PenDown());
586 EXPECT_CALL(turtle, Forward(100));
587 EXPECT_CALL(turtle, PenUp());
593 By creating an object of type `InSequence`, all expectations in its scope are
594 put into a *sequence* and have to occur *sequentially*. Since we are just
595 relying on the constructor and destructor of this object to do the actual work,
596 its name is really irrelevant.
598 In this example, we test that `Foo()` calls the three expected functions in the
599 order as written. If a call is made out-of-order, it will be an error.
601 (What if you care about the relative order of some of the calls, but not all of
602 them? Can you specify an arbitrary partial order? The answer is ... yes! The
603 details can be found [here](cook_book.md#OrderedCalls).)
605 ### All Expectations Are Sticky (Unless Said Otherwise) {#StickyExpectations}
607 Now let's do a quick quiz to see how well you can use this mock stuff already.
608 How would you test that the turtle is asked to go to the origin *exactly twice*
609 (you want to ignore any other instructions it receives)?
611 After you've come up with your answer, take a look at ours and compare notes
612 (solve it yourself first - don't cheat!):
616 using ::testing::AnyNumber;
618 EXPECT_CALL(turtle, GoTo(_, _)) // #1
620 EXPECT_CALL(turtle, GoTo(0, 0)) // #2
624 Suppose `turtle.GoTo(0, 0)` is called three times. In the third time, gMock will
625 see that the arguments match expectation #2 (remember that we always pick the
626 last matching expectation). Now, since we said that there should be only two
627 such calls, gMock will report an error immediately. This is basically what we've
628 told you in the [Using Multiple Expectations](#MultiExpectations) section above.
630 This example shows that **expectations in gMock are "sticky" by default**, in
631 the sense that they remain active even after we have reached their invocation
632 upper bounds. This is an important rule to remember, as it affects the meaning
633 of the spec, and is **different** to how it's done in many other mocking
634 frameworks (Why'd we do that? Because we think our rule makes the common cases
635 easier to express and understand.).
637 Simple? Let's see if you've really understood it: what does the following code
641 using ::testing::Return;
643 for (int i = n; i > 0; i--) {
644 EXPECT_CALL(turtle, GetX())
645 .WillOnce(Return(10*i));
649 If you think it says that `turtle.GetX()` will be called `n` times and will
650 return 10, 20, 30, ..., consecutively, think twice! The problem is that, as we
651 said, expectations are sticky. So, the second time `turtle.GetX()` is called,
652 the last (latest) `EXPECT_CALL()` statement will match, and will immediately
653 lead to an "upper bound violated" error - this piece of code is not very useful!
655 One correct way of saying that `turtle.GetX()` will return 10, 20, 30, ..., is
656 to explicitly say that the expectations are *not* sticky. In other words, they
657 should *retire* as soon as they are saturated:
660 using ::testing::Return;
662 for (int i = n; i > 0; i--) {
663 EXPECT_CALL(turtle, GetX())
664 .WillOnce(Return(10*i))
665 .RetiresOnSaturation();
669 And, there's a better way to do it: in this case, we expect the calls to occur
670 in a specific order, and we line up the actions to match the order. Since the
671 order is important here, we should make it explicit using a sequence:
674 using ::testing::InSequence;
675 using ::testing::Return;
680 for (int i = 1; i <= n; i++) {
681 EXPECT_CALL(turtle, GetX())
682 .WillOnce(Return(10*i))
683 .RetiresOnSaturation();
688 By the way, the other situation where an expectation may *not* be sticky is when
689 it's in a sequence - as soon as another expectation that comes after it in the
690 sequence has been used, it automatically retires (and will never be used to
693 ### Uninteresting Calls
695 A mock object may have many methods, and not all of them are that interesting.
696 For example, in some tests we may not care about how many times `GetX()` and
699 In gMock, if you are not interested in a method, just don't say anything about
700 it. If a call to this method occurs, you'll see a warning in the test output,
701 but it won't be a failure. This is called "naggy" behavior; to change, see
702 [The Nice, the Strict, and the Naggy](cook_book.md#NiceStrictNaggy).