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