3 # Defining a Mock Class #
5 ## Mocking a Normal Class ##
12 virtual int GetSize() const = 0;
13 virtual string Describe(const char* name) = 0;
14 virtual string Describe(int type) = 0;
15 virtual bool Process(Bar elem, int count) = 0;
18 (note that `~Foo()` **must** be virtual) we can define its mock as
20 #include <gmock/gmock.h>
22 class MockFoo : public Foo {
23 MOCK_CONST_METHOD0(GetSize, int());
24 MOCK_METHOD1(Describe, string(const char* name));
25 MOCK_METHOD1(Describe, string(int type));
26 MOCK_METHOD2(Process, bool(Bar elem, int count));
30 To create a "nice" mock object which ignores all uninteresting calls,
31 or a "strict" mock object, which treats them as failures:
33 NiceMock<MockFoo> nice_foo; // The type is a subclass of MockFoo.
34 StrictMock<MockFoo> strict_foo; // The type is a subclass of MockFoo.
37 ## Mocking a Class Template ##
41 template <typename Elem>
42 class StackInterface {
45 virtual ~StackInterface();
46 virtual int GetSize() const = 0;
47 virtual void Push(const Elem& x) = 0;
50 (note that `~StackInterface()` **must** be virtual) just append `_T` to the `MOCK_*` macros:
52 template <typename Elem>
53 class MockStack : public StackInterface<Elem> {
56 MOCK_CONST_METHOD0_T(GetSize, int());
57 MOCK_METHOD1_T(Push, void(const Elem& x));
61 ## Specifying Calling Conventions for Mock Functions ##
63 If your mock function doesn't use the default calling convention, you
64 can specify it by appending `_WITH_CALLTYPE` to any of the macros
65 described in the previous two sections and supplying the calling
66 convention as the first argument to the macro. For example,
68 MOCK_METHOD_1_WITH_CALLTYPE(STDMETHODCALLTYPE, Foo, bool(int n));
69 MOCK_CONST_METHOD2_WITH_CALLTYPE(STDMETHODCALLTYPE, Bar, int(double x, double y));
71 where `STDMETHODCALLTYPE` is defined by `<objbase.h>` on Windows.
73 # Using Mocks in Tests #
76 1. Import the Google Mock names you need to use. All Google Mock names are in the `testing` namespace unless they are macros or otherwise noted.
77 1. Create the mock objects.
78 1. Optionally, set the default actions of the mock objects.
79 1. Set your expectations on the mock objects (How will they be called? What wil they do?).
80 1. Exercise code that uses the mock objects; if necessary, check the result using [Google Test](http://code.google.com/p/googletest/) assertions.
81 1. When a mock objects is destructed, Google Mock automatically verifies that all expectations on it have been satisfied.
85 using ::testing::Return; // #1
87 TEST(BarTest, DoesThis) {
90 ON_CALL(foo, GetSize()) // #3
91 .WillByDefault(Return(1));
92 // ... other default actions ...
94 EXPECT_CALL(foo, Describe(5)) // #4
96 .WillRepeatedly(Return("Category 5"));
97 // ... other expectations ...
99 EXPECT_EQ("good", MyProductionFunction(&foo)); // #5
103 # Setting Default Actions #
105 Google Mock has a **built-in default action** for any function that
106 returns `void`, `bool`, a numeric value, or a pointer.
108 To customize the default action for functions with return type `T` globally:
110 using ::testing::DefaultValue;
112 DefaultValue<T>::Set(value); // Sets the default value to be returned.
113 // ... use the mocks ...
114 DefaultValue<T>::Clear(); // Resets the default value.
117 To customize the default action for a particular method, use `ON_CALL()`:
119 ON_CALL(mock_object, method(matchers))
120 .With(multi_argument_matcher) ?
121 .WillByDefault(action);
124 # Setting Expectations #
126 `EXPECT_CALL()` sets **expectations** on a mock method (How will it be
127 called? What will it do?):
129 EXPECT_CALL(mock_object, method(matchers))
130 .With(multi_argument_matcher) ?
131 .Times(cardinality) ?
132 .InSequence(sequences) *
133 .After(expectations) *
135 .WillRepeatedly(action) ?
136 .RetiresOnSaturation(); ?
139 If `Times()` is omitted, the cardinality is assumed to be:
141 * `Times(1)` when there is neither `WillOnce()` nor `WillRepeatedly()`;
142 * `Times(n)` when there are `n WillOnce()`s but no `WillRepeatedly()`, where `n` >= 1; or
143 * `Times(AtLeast(n))` when there are `n WillOnce()`s and a `WillRepeatedly()`, where `n` >= 0.
145 A method with no `EXPECT_CALL()` is free to be invoked _any number of times_, and the default action will be taken each time.
149 A **matcher** matches a _single_ argument. You can use it inside
150 `ON_CALL()` or `EXPECT_CALL()`, or use it to validate a value
153 | `EXPECT_THAT(value, matcher)` | Asserts that `value` matches `matcher`. |
154 |:------------------------------|:----------------------------------------|
155 | `ASSERT_THAT(value, matcher)` | The same as `EXPECT_THAT(value, matcher)`, except that it generates a **fatal** failure. |
157 Built-in matchers (where `argument` is the function argument) are
158 divided into several categories:
161 |`_`|`argument` can be any value of the correct type.|
162 |:--|:-----------------------------------------------|
163 |`A<type>()` or `An<type>()`|`argument` can be any value of type `type`. |
165 ## Generic Comparison ##
167 |`Eq(value)` or `value`|`argument == value`|
168 |:---------------------|:------------------|
169 |`Ge(value)` |`argument >= value`|
170 |`Gt(value)` |`argument > value` |
171 |`Le(value)` |`argument <= value`|
172 |`Lt(value)` |`argument < value` |
173 |`Ne(value)` |`argument != value`|
174 |`IsNull()` |`argument` is a `NULL` pointer (raw or smart).|
175 |`NotNull()` |`argument` is a non-null pointer (raw or smart).|
176 |`Ref(variable)` |`argument` is a reference to `variable`.|
177 |`TypedEq<type>(value)`|`argument` has type `type` and is equal to `value`. You may need to use this instead of `Eq(value)` when the mock function is overloaded.|
179 Except `Ref()`, these matchers make a _copy_ of `value` in case it's
180 modified or destructed later. If the compiler complains that `value`
181 doesn't have a public copy constructor, try wrap it in `ByRef()`,
182 e.g. `Eq(ByRef(non_copyable_value))`. If you do that, make sure
183 `non_copyable_value` is not changed afterwards, or the meaning of your
184 matcher will be changed.
186 ## Floating-Point Matchers ##
188 |`DoubleEq(a_double)`|`argument` is a `double` value approximately equal to `a_double`, treating two NaNs as unequal.|
189 |:-------------------|:----------------------------------------------------------------------------------------------|
190 |`FloatEq(a_float)` |`argument` is a `float` value approximately equal to `a_float`, treating two NaNs as unequal. |
191 |`NanSensitiveDoubleEq(a_double)`|`argument` is a `double` value approximately equal to `a_double`, treating two NaNs as equal. |
192 |`NanSensitiveFloatEq(a_float)`|`argument` is a `float` value approximately equal to `a_float`, treating two NaNs as equal. |
194 The above matchers use ULP-based comparison (the same as used in
195 [Google Test](http://code.google.com/p/googletest/)). They
196 automatically pick a reasonable error bound based on the absolute
197 value of the expected value. `DoubleEq()` and `FloatEq()` conform to
198 the IEEE standard, which requires comparing two NaNs for equality to
199 return false. The `NanSensitive*` version instead treats two NaNs as
200 equal, which is often what a user wants.
202 ## String Matchers ##
204 The `argument` can be either a C string or a C++ string object:
206 |`ContainsRegex(string)`|`argument` matches the given regular expression.|
207 |:----------------------|:-----------------------------------------------|
208 |`EndsWith(suffix)` |`argument` ends with string `suffix`. |
209 |`HasSubstr(string)` |`argument` contains `string` as a sub-string. |
210 |`MatchesRegex(string)` |`argument` matches the given regular expression with the match starting at the first character and ending at the last character.|
211 |`StartsWith(prefix)` |`argument` starts with string `prefix`. |
212 |`StrCaseEq(string)` |`argument` is equal to `string`, ignoring case. |
213 |`StrCaseNe(string)` |`argument` is not equal to `string`, ignoring case.|
214 |`StrEq(string)` |`argument` is equal to `string`. |
215 |`StrNe(string)` |`argument` is not equal to `string`. |
217 `StrCaseEq()`, `StrCaseNe()`, `StrEq()`, and `StrNe()` work for wide
220 ## Container Matchers ##
222 Most STL-style containers support `==`, so you can use
223 `Eq(expected_container)` or simply `expected_container` to match a
224 container exactly. If you want to write the elements in-line,
225 match them more flexibly, or get more informative messages, you can use:
227 | `Contains(e)` | `argument` contains an element that matches `e`, which can be either a value or a matcher. |
228 |:--------------|:-------------------------------------------------------------------------------------------|
229 |`ElementsAre(e0, e1, ..., en)`|`argument` has `n + 1` elements, where the i-th element matches `ei`, which can be a value or a matcher. 0 to 10 arguments are allowed.|
230 |`ElementsAreArray(array)` or `ElementsAreArray(array, count)`|The same as `ElementsAre()` except that the expected element values/matchers come from a C-style array.|
231 | `ContainerEq(container)` | The same as `Eq(container)` except that the failure message also includes which elements are in one container but not the other. |
233 These matchers can also match:
235 1. a native array passed by reference (e.g. in `Foo(const int (&a)[5])`), and
236 1. an array passed as a pointer and a count (e.g. in `Bar(const T* buffer, int len)` -- see [Multi-argument Matchers](#Multiargument_Matchers.md)).
238 where the array may be multi-dimensional (i.e. its elements can be arrays).
240 ## Member Matchers ##
242 |`Field(&class::field, m)`|`argument.field` (or `argument->field` when `argument` is a plain pointer) matches matcher `m`, where `argument` is an object of type _class_.|
243 |:------------------------|:---------------------------------------------------------------------------------------------------------------------------------------------|
244 |`Key(e)` |`argument.first` matches `e`, which can be either a value or a matcher. E.g. `Contains(Key(Le(5)))` can verify that a `map` contains a key `<= 5`.|
245 |`Pair(m1, m2)` |`argument` is an `std::pair` whose `first` field matches `m1` and `second` field matches `m2`. |
246 |`Property(&class::property, m)`|`argument.property()` (or `argument->property()` when `argument` is a plain pointer) matches matcher `m`, where `argument` is an object of type _class_.|
248 ## Matching the Result of a Function or Functor ##
250 |`ResultOf(f, m)`|`f(argument)` matches matcher `m`, where `f` is a function or functor.|
251 |:---------------|:---------------------------------------------------------------------|
253 ## Pointer Matchers ##
255 |`Pointee(m)`|`argument` (either a smart pointer or a raw pointer) points to a value that matches matcher `m`.|
256 |:-----------|:-----------------------------------------------------------------------------------------------|
258 ## Multiargument Matchers ##
260 These are matchers on tuple types. They can be used in
261 `.With()`. The following can be used on functions with <i>two<br>
262 arguments</i> `x` and `y`:
272 You can use the following selectors to pick a subset of the arguments
273 (or reorder them) to participate in the matching:
275 |`AllArgs(m)`|Equivalent to `m`. Useful as syntactic sugar in `.With(AllArgs(m))`.|
276 |:-----------|:-------------------------------------------------------------------|
277 |`Args<N1, N2, ..., Nk>(m)`|The `k` selected (using 0-based indices) arguments match `m`, e.g. `Args<1, 2>(Contains(5))`.|
279 ## Composite Matchers ##
281 You can make a matcher from one or more other matchers:
283 |`AllOf(m1, m2, ..., mn)`|`argument` matches all of the matchers `m1` to `mn`.|
284 |:-----------------------|:---------------------------------------------------|
285 |`AnyOf(m1, m2, ..., mn)`|`argument` matches at least one of the matchers `m1` to `mn`.|
286 |`Not(m)` |`argument` doesn't match matcher `m`. |
288 ## Adapters for Matchers ##
290 |`MatcherCast<T>(m)`|casts matcher `m` to type `Matcher<T>`.|
291 |:------------------|:--------------------------------------|
292 |`SafeMatcherCast<T>(m)`| [safely casts](V1_5_CookBook#Casting_Matchers.md) matcher `m` to type `Matcher<T>`. |
293 |`Truly(predicate)` |`predicate(argument)` returns something considered by C++ to be true, where `predicate` is a function or functor.|
295 ## Matchers as Predicates ##
297 |`Matches(m)`|a unary functor that returns `true` if the argument matches `m`.|
298 |:-----------|:---------------------------------------------------------------|
299 |`ExplainMatchResult(m, value, result_listener)`|returns `true` if `value` matches `m`, explaining the result to `result_listener`.|
300 |`Value(x, m)`|returns `true` if the value of `x` matches `m`. |
302 ## Defining Matchers ##
304 | `MATCHER(IsEven, "") { return (arg % 2) == 0; }` | Defines a matcher `IsEven()` to match an even number. |
305 |:-------------------------------------------------|:------------------------------------------------------|
306 | `MATCHER_P(IsDivisibleBy, n, "") { *result_listener << "where the remainder is " << (arg % n); return (arg % n) == 0; }` | Defines a macher `IsDivisibleBy(n)` to match a number divisible by `n`. |
307 | `MATCHER_P2(IsBetween, a, b, "is between %(a)s and %(b)s") { return a <= arg && arg <= b; }` | Defines a matcher `IsBetween(a, b)` to match a value in the range [`a`, `b`]. |
311 1. The `MATCHER*` macros cannot be used inside a function or class.
312 1. The matcher body must be _purely functional_ (i.e. it cannot have any side effect, and the result must not depend on anything other than the value being matched and the matcher parameters).
313 1. You can use `PrintToString(x)` to convert a value `x` of any type to a string.
315 ## Matchers as Test Assertions ##
317 |`ASSERT_THAT(expression, m)`|Generates a [fatal failure](http://code.google.com/p/googletest/wiki/GoogleTestPrimer#Assertions) if the value of `expression` doesn't match matcher `m`.|
318 |:---------------------------|:--------------------------------------------------------------------------------------------------------------------------------------------------------|
319 |`EXPECT_THAT(expression, m)`|Generates a non-fatal failure if the value of `expression` doesn't match matcher `m`. |
323 **Actions** specify what a mock function should do when invoked.
325 ## Returning a Value ##
327 |`Return()`|Return from a `void` mock function.|
328 |:---------|:----------------------------------|
329 |`Return(value)`|Return `value`. |
330 |`ReturnArg<N>()`|Return the `N`-th (0-based) argument.|
331 |`ReturnNew<T>(a1, ..., ak)`|Return `new T(a1, ..., ak)`; a different object is created each time.|
332 |`ReturnNull()`|Return a null pointer. |
333 |`ReturnRef(variable)`|Return a reference to `variable`. |
337 |`Assign(&variable, value)`|Assign `value` to variable.|
338 |:-------------------------|:--------------------------|
339 | `DeleteArg<N>()` | Delete the `N`-th (0-based) argument, which must be a pointer. |
340 | `SaveArg<N>(pointer)` | Save the `N`-th (0-based) argument to `*pointer`. |
341 | `SetArgReferee<N>(value)` | Assign value to the variable referenced by the `N`-th (0-based) argument. |
342 |`SetArgumentPointee<N>(value)`|Assign `value` to the variable pointed by the `N`-th (0-based) argument.|
343 |`SetArrayArgument<N>(first, last)`|Copies the elements in source range [`first`, `last`) to the array pointed to by the `N`-th (0-based) argument, which can be either a pointer or an iterator. The action does not take ownership of the elements in the source range.|
344 |`SetErrnoAndReturn(error, value)`|Set `errno` to `error` and return `value`.|
345 |`Throw(exception)` |Throws the given exception, which can be any copyable value. Available since v1.1.0.|
347 ## Using a Function or a Functor as an Action ##
349 |`Invoke(f)`|Invoke `f` with the arguments passed to the mock function, where `f` can be a global/static function or a functor.|
350 |:----------|:-----------------------------------------------------------------------------------------------------------------|
351 |`Invoke(object_pointer, &class::method)`|Invoke the {method on the object with the arguments passed to the mock function. |
352 |`InvokeWithoutArgs(f)`|Invoke `f`, which can be a global/static function or a functor. `f` must take no arguments. |
353 |`InvokeWithoutArgs(object_pointer, &class::method)`|Invoke the method on the object, which takes no arguments. |
354 |`InvokeArgument<N>(arg1, arg2, ..., argk)`|Invoke the mock function's `N`-th (0-based) argument, which must be a function or a functor, with the `k` arguments.|
356 The return value of the invoked function is used as the return value
359 When defining a function or functor to be used with `Invoke*()`, you can declare any unused parameters as `Unused`:
361 double Distance(Unused, double x, double y) { return sqrt(x*x + y*y); }
363 EXPECT_CALL(mock, Foo("Hi", _, _)).WillOnce(Invoke(Distance));
366 In `InvokeArgument<N>(...)`, if an argument needs to be passed by reference, wrap it inside `ByRef()`. For example,
368 InvokeArgument<2>(5, string("Hi"), ByRef(foo))
370 calls the mock function's #2 argument, passing to it `5` and `string("Hi")` by value, and `foo` by reference.
374 |`DoDefault()`|Do the default action (specified by `ON_CALL()` or the built-in one).|
375 |:------------|:--------------------------------------------------------------------|
377 **Note:** due to technical reasons, `DoDefault()` cannot be used inside a composite action - trying to do so will result in a run-time error.
379 ## Composite Actions ##
381 |`DoAll(a1, a2, ..., an)`|Do all actions `a1` to `an` and return the result of `an` in each invocation. The first `n - 1` sub-actions must return void. |
382 |:-----------------------|:-----------------------------------------------------------------------------------------------------------------------------|
383 |`IgnoreResult(a)` |Perform action `a` and ignore its result. `a` must not return void. |
384 |`WithArg<N>(a)` |Pass the `N`-th (0-based) argument of the mock function to action `a` and perform it. |
385 |`WithArgs<N1, N2, ..., Nk>(a)`|Pass the selected (0-based) arguments of the mock function to action `a` and perform it. |
386 |`WithoutArgs(a)` |Perform action `a` without any arguments. |
388 ## Defining Actions ##
390 | `ACTION(Sum) { return arg0 + arg1; }` | Defines an action `Sum()` to return the sum of the mock function's argument #0 and #1. |
391 |:--------------------------------------|:---------------------------------------------------------------------------------------|
392 | `ACTION_P(Plus, n) { return arg0 + n; }` | Defines an action `Plus(n)` to return the sum of the mock function's argument #0 and `n`. |
393 | `ACTION_Pk(Foo, p1, ..., pk) { statements; }` | Defines a parameterized action `Foo(p1, ..., pk)` to execute the given `statements`. |
395 The `ACTION*` macros cannot be used inside a function or class.
399 These are used in `Times()` to specify how many times a mock function will be called:
401 |`AnyNumber()`|The function can be called any number of times.|
402 |:------------|:----------------------------------------------|
403 |`AtLeast(n)` |The call is expected at least `n` times. |
404 |`AtMost(n)` |The call is expected at most `n` times. |
405 |`Between(m, n)`|The call is expected between `m` and `n` (inclusive) times.|
406 |`Exactly(n) or n`|The call is expected exactly `n` times. In particular, the call should never happen when `n` is 0.|
408 # Expectation Order #
410 By default, the expectations can be matched in _any_ order. If some
411 or all expectations must be matched in a given order, there are two
412 ways to specify it. They can be used either independently or
415 ## The After Clause ##
418 using ::testing::Expectation;
420 Expectation init_x = EXPECT_CALL(foo, InitX());
421 Expectation init_y = EXPECT_CALL(foo, InitY());
422 EXPECT_CALL(foo, Bar())
423 .After(init_x, init_y);
425 says that `Bar()` can be called only after both `InitX()` and
426 `InitY()` have been called.
428 If you don't know how many pre-requisites an expectation has when you
429 write it, you can use an `ExpectationSet` to collect them:
432 using ::testing::ExpectationSet;
434 ExpectationSet all_inits;
435 for (int i = 0; i < element_count; i++) {
436 all_inits += EXPECT_CALL(foo, InitElement(i));
438 EXPECT_CALL(foo, Bar())
441 says that `Bar()` can be called only after all elements have been
442 initialized (but we don't care about which elements get initialized
445 Modifying an `ExpectationSet` after using it in an `.After()` doesn't
446 affect the meaning of the `.After()`.
450 When you have a long chain of sequential expectations, it's easier to
451 specify the order using **sequences**, which don't require you to given
452 each expectation in the chain a different name. <i>All expected<br>
453 calls</i> in the same sequence must occur in the order they are
457 using ::testing::Sequence;
460 EXPECT_CALL(foo, Reset())
462 .WillOnce(Return(true));
463 EXPECT_CALL(foo, GetSize())
465 .WillOnce(Return(1));
466 EXPECT_CALL(foo, Describe(A<const char*>()))
468 .WillOnce(Return("dummy"));
470 says that `Reset()` must be called before _both_ `GetSize()` _and_
471 `Describe()`, and the latter two can occur in any order.
473 To put many expectations in a sequence conveniently:
475 using ::testing::InSequence;
485 says that all expected calls in the scope of `dummy` must occur in
486 strict order. The name `dummy` is irrelevant.)
488 # Verifying and Resetting a Mock #
490 Google Mock will verify the expectations on a mock object when it is destructed, or you can do it earlier:
492 using ::testing::Mock;
494 // Verifies and removes the expectations on mock_obj;
495 // returns true iff successful.
496 Mock::VerifyAndClearExpectations(&mock_obj);
498 // Verifies and removes the expectations on mock_obj;
499 // also removes the default actions set by ON_CALL();
500 // returns true iff successful.
501 Mock::VerifyAndClear(&mock_obj);
504 You can also tell Google Mock that a mock object can be leaked and doesn't
507 Mock::AllowLeak(&mock_obj);
512 Google Mock defines a convenient mock class template
514 class MockFunction<R(A1, ..., An)> {
516 MOCK_METHODn(Call, R(A1, ..., An));
519 See this [recipe](V1_5_CookBook#Using_Check_Points.md) for one application of it.
523 | `--gmock_catch_leaked_mocks=0` | Don't report leaked mock objects as failures. |
524 |:-------------------------------|:----------------------------------------------|
525 | `--gmock_verbose=LEVEL` | Sets the default verbosity level (`info`, `warning`, or `error`) of Google Mock messages. |