1
2
3# Defining a Mock Class #
4
5## Mocking a Normal Class ##
6
7Given
8```
9class Foo {
10  ...
11  virtual ~Foo();
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;
16};
17```
18(note that `~Foo()` **must** be virtual) we can define its mock as
19```
20#include "gmock/gmock.h"
21
22class 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));
27};
28```
29
30To create a "nice" mock object which ignores all uninteresting calls,
31or a "strict" mock object, which treats them as failures:
32```
33NiceMock<MockFoo> nice_foo;     // The type is a subclass of MockFoo.
34StrictMock<MockFoo> strict_foo; // The type is a subclass of MockFoo.
35```
36
37## Mocking a Class Template ##
38
39To mock
40```
41template <typename Elem>
42class StackInterface {
43 public:
44  ...
45  virtual ~StackInterface();
46  virtual int GetSize() const = 0;
47  virtual void Push(const Elem& x) = 0;
48};
49```
50(note that `~StackInterface()` **must** be virtual) just append `_T` to the `MOCK_*` macros:
51```
52template <typename Elem>
53class MockStack : public StackInterface<Elem> {
54 public:
55  ...
56  MOCK_CONST_METHOD0_T(GetSize, int());
57  MOCK_METHOD1_T(Push, void(const Elem& x));
58};
59```
60
61## Specifying Calling Conventions for Mock Functions ##
62
63If your mock function doesn't use the default calling convention, you
64can specify it by appending `_WITH_CALLTYPE` to any of the macros
65described in the previous two sections and supplying the calling
66convention as the first argument to the macro. For example,
67```
68  MOCK_METHOD_1_WITH_CALLTYPE(STDMETHODCALLTYPE, Foo, bool(int n));
69  MOCK_CONST_METHOD2_WITH_CALLTYPE(STDMETHODCALLTYPE, Bar, int(double x, double y));
70```
71where `STDMETHODCALLTYPE` is defined by `<objbase.h>` on Windows.
72
73# Using Mocks in Tests #
74
75The typical flow is:
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](../../googletest/) assertions.
81  1. When a mock objects is destructed, Google Mock automatically verifies that all expectations on it have been satisfied.
82
83Here is an example:
84```
85using ::testing::Return;                            // #1
86
87TEST(BarTest, DoesThis) {
88  MockFoo foo;                                    // #2
89
90  ON_CALL(foo, GetSize())                         // #3
91      .WillByDefault(Return(1));
92  // ... other default actions ...
93
94  EXPECT_CALL(foo, Describe(5))                   // #4
95      .Times(3)
96      .WillRepeatedly(Return("Category 5"));
97  // ... other expectations ...
98
99  EXPECT_EQ("good", MyProductionFunction(&foo));  // #5
100}                                                 // #6
101```
102
103# Setting Default Actions #
104
105Google Mock has a **built-in default action** for any function that
106returns `void`, `bool`, a numeric value, or a pointer.
107
108To customize the default action for functions with return type `T` globally:
109```
110using ::testing::DefaultValue;
111
112// Sets the default value to be returned. T must be CopyConstructible.
113DefaultValue<T>::Set(value);
114// Sets a factory. Will be invoked on demand. T must be MoveConstructible.
115//   T MakeT();
116DefaultValue<T>::SetFactory(&MakeT);
117// ... use the mocks ...
118// Resets the default value.
119DefaultValue<T>::Clear();
120```
121
122To customize the default action for a particular method, use `ON_CALL()`:
123```
124ON_CALL(mock_object, method(matchers))
125    .With(multi_argument_matcher)  ?
126    .WillByDefault(action);
127```
128
129# Setting Expectations #
130
131`EXPECT_CALL()` sets **expectations** on a mock method (How will it be
132called? What will it do?):
133```
134EXPECT_CALL(mock_object, method(matchers))
135    .With(multi_argument_matcher)  ?
136    .Times(cardinality)            ?
137    .InSequence(sequences)         *
138    .After(expectations)           *
139    .WillOnce(action)              *
140    .WillRepeatedly(action)        ?
141    .RetiresOnSaturation();        ?
142```
143
144If `Times()` is omitted, the cardinality is assumed to be:
145
146  * `Times(1)` when there is neither `WillOnce()` nor `WillRepeatedly()`;
147  * `Times(n)` when there are `n WillOnce()`s but no `WillRepeatedly()`, where `n` >= 1; or
148  * `Times(AtLeast(n))` when there are `n WillOnce()`s and a `WillRepeatedly()`, where `n` >= 0.
149
150A method with no `EXPECT_CALL()` is free to be invoked _any number of times_, and the default action will be taken each time.
151
152# Matchers #
153
154A **matcher** matches a _single_ argument.  You can use it inside
155`ON_CALL()` or `EXPECT_CALL()`, or use it to validate a value
156directly:
157
158| `EXPECT_THAT(value, matcher)` | Asserts that `value` matches `matcher`. |
159|:------------------------------|:----------------------------------------|
160| `ASSERT_THAT(value, matcher)` | The same as `EXPECT_THAT(value, matcher)`, except that it generates a **fatal** failure. |
161
162Built-in matchers (where `argument` is the function argument) are
163divided into several categories:
164
165## Wildcard ##
166|`_`|`argument` can be any value of the correct type.|
167|:--|:-----------------------------------------------|
168|`A<type>()` or `An<type>()`|`argument` can be any value of type `type`.     |
169
170## Generic Comparison ##
171
172|`Eq(value)` or `value`|`argument == value`|
173|:---------------------|:------------------|
174|`Ge(value)`           |`argument >= value`|
175|`Gt(value)`           |`argument > value` |
176|`Le(value)`           |`argument <= value`|
177|`Lt(value)`           |`argument < value` |
178|`Ne(value)`           |`argument != value`|
179|`IsNull()`            |`argument` is a `NULL` pointer (raw or smart).|
180|`NotNull()`           |`argument` is a non-null pointer (raw or smart).|
181|`Ref(variable)`       |`argument` is a reference to `variable`.|
182|`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.|
183
184Except `Ref()`, these matchers make a _copy_ of `value` in case it's
185modified or destructed later. If the compiler complains that `value`
186doesn't have a public copy constructor, try wrap it in `ByRef()`,
187e.g. `Eq(ByRef(non_copyable_value))`. If you do that, make sure
188`non_copyable_value` is not changed afterwards, or the meaning of your
189matcher will be changed.
190
191## Floating-Point Matchers ##
192
193|`DoubleEq(a_double)`|`argument` is a `double` value approximately equal to `a_double`, treating two NaNs as unequal.|
194|:-------------------|:----------------------------------------------------------------------------------------------|
195|`FloatEq(a_float)`  |`argument` is a `float` value approximately equal to `a_float`, treating two NaNs as unequal.  |
196|`NanSensitiveDoubleEq(a_double)`|`argument` is a `double` value approximately equal to `a_double`, treating two NaNs as equal.  |
197|`NanSensitiveFloatEq(a_float)`|`argument` is a `float` value approximately equal to `a_float`, treating two NaNs as equal.    |
198
199The above matchers use ULP-based comparison (the same as used in
200[Google Test](../../googletest/)). They
201automatically pick a reasonable error bound based on the absolute
202value of the expected value.  `DoubleEq()` and `FloatEq()` conform to
203the IEEE standard, which requires comparing two NaNs for equality to
204return false. The `NanSensitive*` version instead treats two NaNs as
205equal, which is often what a user wants.
206
207|`DoubleNear(a_double, max_abs_error)`|`argument` is a `double` value close to `a_double` (absolute error <= `max_abs_error`), treating two NaNs as unequal.|
208|:------------------------------------|:--------------------------------------------------------------------------------------------------------------------|
209|`FloatNear(a_float, max_abs_error)`  |`argument` is a `float` value close to `a_float` (absolute error <= `max_abs_error`), treating two NaNs as unequal.  |
210|`NanSensitiveDoubleNear(a_double, max_abs_error)`|`argument` is a `double` value close to `a_double` (absolute error <= `max_abs_error`), treating two NaNs as equal.  |
211|`NanSensitiveFloatNear(a_float, max_abs_error)`|`argument` is a `float` value close to `a_float` (absolute error <= `max_abs_error`), treating two NaNs as equal.    |
212
213## String Matchers ##
214
215The `argument` can be either a C string or a C++ string object:
216
217|`ContainsRegex(string)`|`argument` matches the given regular expression.|
218|:----------------------|:-----------------------------------------------|
219|`EndsWith(suffix)`     |`argument` ends with string `suffix`.           |
220|`HasSubstr(string)`    |`argument` contains `string` as a sub-string.   |
221|`MatchesRegex(string)` |`argument` matches the given regular expression with the match starting at the first character and ending at the last character.|
222|`StartsWith(prefix)`   |`argument` starts with string `prefix`.         |
223|`StrCaseEq(string)`    |`argument` is equal to `string`, ignoring case. |
224|`StrCaseNe(string)`    |`argument` is not equal to `string`, ignoring case.|
225|`StrEq(string)`        |`argument` is equal to `string`.                |
226|`StrNe(string)`        |`argument` is not equal to `string`.            |
227
228`ContainsRegex()` and `MatchesRegex()` use the regular expression
229syntax defined
230[here](../../googletest/docs/AdvancedGuide.md#regular-expression-syntax).
231`StrCaseEq()`, `StrCaseNe()`, `StrEq()`, and `StrNe()` work for wide
232strings as well.
233
234## Container Matchers ##
235
236Most STL-style containers support `==`, so you can use
237`Eq(expected_container)` or simply `expected_container` to match a
238container exactly.   If you want to write the elements in-line,
239match them more flexibly, or get more informative messages, you can use:
240
241| `ContainerEq(container)` | The same as `Eq(container)` except that the failure message also includes which elements are in one container but not the other. |
242|:-------------------------|:---------------------------------------------------------------------------------------------------------------------------------|
243| `Contains(e)`            | `argument` contains an element that matches `e`, which can be either a value or a matcher.                                       |
244| `Each(e)`                | `argument` is a container where _every_ element matches `e`, which can be either a value or a matcher.                           |
245| `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. |
246| `ElementsAreArray({ e0, e1, ..., en })`, `ElementsAreArray(array)`, or `ElementsAreArray(array, count)` | The same as `ElementsAre()` except that the expected element values/matchers come from an initializer list, STL-style container, or C-style array. |
247| `IsEmpty()`              | `argument` is an empty container (`container.empty()`).                                                                          |
248| `Pointwise(m, container)` | `argument` contains the same number of elements as in `container`, and for all i, (the i-th element in `argument`, the i-th element in `container`) match `m`, which is a matcher on 2-tuples. E.g. `Pointwise(Le(), upper_bounds)` verifies that each element in `argument` doesn't exceed the corresponding element in `upper_bounds`. See more detail below. |
249| `SizeIs(m)`              | `argument` is a container whose size matches `m`. E.g. `SizeIs(2)` or `SizeIs(Lt(2))`.                                           |
250| `UnorderedElementsAre(e0, e1, ..., en)` | `argument` has `n + 1` elements, and under some permutation each element matches an `ei` (for a different `i`), which can be a value or a matcher. 0 to 10 arguments are allowed. |
251| `UnorderedElementsAreArray({ e0, e1, ..., en })`, `UnorderedElementsAreArray(array)`, or `UnorderedElementsAreArray(array, count)` | The same as `UnorderedElementsAre()` except that the expected element values/matchers come from an initializer list, STL-style container, or C-style array. |
252| `WhenSorted(m)`          | When `argument` is sorted using the `<` operator, it matches container matcher `m`. E.g. `WhenSorted(UnorderedElementsAre(1, 2, 3))` verifies that `argument` contains elements `1`, `2`, and `3`, ignoring order. |
253| `WhenSortedBy(comparator, m)` | The same as `WhenSorted(m)`, except that the given comparator instead of `<` is used to sort `argument`. E.g. `WhenSortedBy(std::greater<int>(), ElementsAre(3, 2, 1))`. |
254
255Notes:
256
257  * These matchers can also match:
258    1. a native array passed by reference (e.g. in `Foo(const int (&a)[5])`), and
259    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)).
260  * The array being matched may be multi-dimensional (i.e. its elements can be arrays).
261  * `m` in `Pointwise(m, ...)` should be a matcher for `::testing::tuple<T, U>` where `T` and `U` are the element type of the actual container and the expected container, respectively. For example, to compare two `Foo` containers where `Foo` doesn't support `operator==` but has an `Equals()` method, one might write:
262
263```
264using ::testing::get;
265MATCHER(FooEq, "") {
266  return get<0>(arg).Equals(get<1>(arg));
267}
268...
269EXPECT_THAT(actual_foos, Pointwise(FooEq(), expected_foos));
270```
271
272## Member Matchers ##
273
274|`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_.|
275|:------------------------|:---------------------------------------------------------------------------------------------------------------------------------------------|
276|`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`.|
277|`Pair(m1, m2)`           |`argument` is an `std::pair` whose `first` field matches `m1` and `second` field matches `m2`.                                                |
278|`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_.|
279
280## Matching the Result of a Function or Functor ##
281
282|`ResultOf(f, m)`|`f(argument)` matches matcher `m`, where `f` is a function or functor.|
283|:---------------|:---------------------------------------------------------------------|
284
285## Pointer Matchers ##
286
287|`Pointee(m)`|`argument` (either a smart pointer or a raw pointer) points to a value that matches matcher `m`.|
288|:-----------|:-----------------------------------------------------------------------------------------------|
289|`WhenDynamicCastTo<T>(m)`| when `argument` is passed through `dynamic_cast<T>()`, it matches matcher `m`.                 |
290
291## Multiargument Matchers ##
292
293Technically, all matchers match a _single_ value. A "multi-argument"
294matcher is just one that matches a _tuple_. The following matchers can
295be used to match a tuple `(x, y)`:
296
297|`Eq()`|`x == y`|
298|:-----|:-------|
299|`Ge()`|`x >= y`|
300|`Gt()`|`x > y` |
301|`Le()`|`x <= y`|
302|`Lt()`|`x < y` |
303|`Ne()`|`x != y`|
304
305You can use the following selectors to pick a subset of the arguments
306(or reorder them) to participate in the matching:
307
308|`AllArgs(m)`|Equivalent to `m`. Useful as syntactic sugar in `.With(AllArgs(m))`.|
309|:-----------|:-------------------------------------------------------------------|
310|`Args<N1, N2, ..., Nk>(m)`|The tuple of the `k` selected (using 0-based indices) arguments matches `m`, e.g. `Args<1, 2>(Eq())`.|
311
312## Composite Matchers ##
313
314You can make a matcher from one or more other matchers:
315
316|`AllOf(m1, m2, ..., mn)`|`argument` matches all of the matchers `m1` to `mn`.|
317|:-----------------------|:---------------------------------------------------|
318|`AnyOf(m1, m2, ..., mn)`|`argument` matches at least one of the matchers `m1` to `mn`.|
319|`Not(m)`                |`argument` doesn't match matcher `m`.               |
320
321## Adapters for Matchers ##
322
323|`MatcherCast<T>(m)`|casts matcher `m` to type `Matcher<T>`.|
324|:------------------|:--------------------------------------|
325|`SafeMatcherCast<T>(m)`| [safely casts](CookBook.md#casting-matchers) matcher `m` to type `Matcher<T>`. |
326|`Truly(predicate)` |`predicate(argument)` returns something considered by C++ to be true, where `predicate` is a function or functor.|
327
328## Matchers as Predicates ##
329
330|`Matches(m)(value)`|evaluates to `true` if `value` matches `m`. You can use `Matches(m)` alone as a unary functor.|
331|:------------------|:---------------------------------------------------------------------------------------------|
332|`ExplainMatchResult(m, value, result_listener)`|evaluates to `true` if `value` matches `m`, explaining the result to `result_listener`.       |
333|`Value(value, m)`  |evaluates to `true` if `value` matches `m`.                                                   |
334
335## Defining Matchers ##
336
337| `MATCHER(IsEven, "") { return (arg % 2) == 0; }` | Defines a matcher `IsEven()` to match an even number. |
338|:-------------------------------------------------|:------------------------------------------------------|
339| `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`. |
340| `MATCHER_P2(IsBetween, a, b, std::string(negation ? "isn't" : "is") + " between " + PrintToString(a) + " and " + PrintToString(b)) { return a <= arg && arg <= b; }` | Defines a matcher `IsBetween(a, b)` to match a value in the range [`a`, `b`]. |
341
342**Notes:**
343
344  1. The `MATCHER*` macros cannot be used inside a function or class.
345  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).
346  1. You can use `PrintToString(x)` to convert a value `x` of any type to a string.
347
348## Matchers as Test Assertions ##
349
350|`ASSERT_THAT(expression, m)`|Generates a [fatal failure](../../googletest/docs/Primer.md#assertions) if the value of `expression` doesn't match matcher `m`.|
351|:---------------------------|:----------------------------------------------------------------------------------------------------------------------------------------------|
352|`EXPECT_THAT(expression, m)`|Generates a non-fatal failure if the value of `expression` doesn't match matcher `m`.                                                          |
353
354# Actions #
355
356**Actions** specify what a mock function should do when invoked.
357
358## Returning a Value ##
359
360|`Return()`|Return from a `void` mock function.|
361|:---------|:----------------------------------|
362|`Return(value)`|Return `value`. If the type of `value` is different to the mock function's return type, `value` is converted to the latter type <i>at the time the expectation is set</i>, not when the action is executed.|
363|`ReturnArg<N>()`|Return the `N`-th (0-based) argument.|
364|`ReturnNew<T>(a1, ..., ak)`|Return `new T(a1, ..., ak)`; a different object is created each time.|
365|`ReturnNull()`|Return a null pointer.             |
366|`ReturnPointee(ptr)`|Return the value pointed to by `ptr`.|
367|`ReturnRef(variable)`|Return a reference to `variable`.  |
368|`ReturnRefOfCopy(value)`|Return a reference to a copy of `value`; the copy lives as long as the action.|
369
370## Side Effects ##
371
372|`Assign(&variable, value)`|Assign `value` to variable.|
373|:-------------------------|:--------------------------|
374| `DeleteArg<N>()`         | Delete the `N`-th (0-based) argument, which must be a pointer. |
375| `SaveArg<N>(pointer)`    | Save the `N`-th (0-based) argument to `*pointer`. |
376| `SaveArgPointee<N>(pointer)` | Save the value pointed to by the `N`-th (0-based) argument to `*pointer`. |
377| `SetArgReferee<N>(value)` |	Assign value to the variable referenced by the `N`-th (0-based) argument. |
378|`SetArgPointee<N>(value)` |Assign `value` to the variable pointed by the `N`-th (0-based) argument.|
379|`SetArgumentPointee<N>(value)`|Same as `SetArgPointee<N>(value)`. Deprecated. Will be removed in v1.7.0.|
380|`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.|
381|`SetErrnoAndReturn(error, value)`|Set `errno` to `error` and return `value`.|
382|`Throw(exception)`        |Throws the given exception, which can be any copyable value. Available since v1.1.0.|
383
384## Using a Function or a Functor as an Action ##
385
386|`Invoke(f)`|Invoke `f` with the arguments passed to the mock function, where `f` can be a global/static function or a functor.|
387|:----------|:-----------------------------------------------------------------------------------------------------------------|
388|`Invoke(object_pointer, &class::method)`|Invoke the {method on the object with the arguments passed to the mock function.                                  |
389|`InvokeWithoutArgs(f)`|Invoke `f`, which can be a global/static function or a functor. `f` must take no arguments.                       |
390|`InvokeWithoutArgs(object_pointer, &class::method)`|Invoke the method on the object, which takes no arguments.                                                        |
391|`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.|
392
393The return value of the invoked function is used as the return value
394of the action.
395
396When defining a function or functor to be used with `Invoke*()`, you can declare any unused parameters as `Unused`:
397```
398  double Distance(Unused, double x, double y) { return sqrt(x*x + y*y); }
399  ...
400  EXPECT_CALL(mock, Foo("Hi", _, _)).WillOnce(Invoke(Distance));
401```
402
403In `InvokeArgument<N>(...)`, if an argument needs to be passed by reference, wrap it inside `ByRef()`. For example,
404```
405  InvokeArgument<2>(5, string("Hi"), ByRef(foo))
406```
407calls the mock function's #2 argument, passing to it `5` and `string("Hi")` by value, and `foo` by reference.
408
409## Default Action ##
410
411|`DoDefault()`|Do the default action (specified by `ON_CALL()` or the built-in one).|
412|:------------|:--------------------------------------------------------------------|
413
414**Note:** due to technical reasons, `DoDefault()` cannot be used inside  a composite action - trying to do so will result in a run-time error.
415
416## Composite Actions ##
417
418|`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. |
419|:-----------------------|:-----------------------------------------------------------------------------------------------------------------------------|
420|`IgnoreResult(a)`       |Perform action `a` and ignore its result. `a` must not return void.                                                           |
421|`WithArg<N>(a)`         |Pass the `N`-th (0-based) argument of the mock function to action `a` and perform it.                                         |
422|`WithArgs<N1, N2, ..., Nk>(a)`|Pass the selected (0-based) arguments of the mock function to action `a` and perform it.                                      |
423|`WithoutArgs(a)`        |Perform action `a` without any arguments.                                                                                     |
424
425## Defining Actions ##
426
427| `ACTION(Sum) { return arg0 + arg1; }` | Defines an action `Sum()` to return the sum of the mock function's argument #0 and #1. |
428|:--------------------------------------|:---------------------------------------------------------------------------------------|
429| `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`. |
430| `ACTION_Pk(Foo, p1, ..., pk) { statements; }` | Defines a parameterized action `Foo(p1, ..., pk)` to execute the given `statements`.   |
431
432The `ACTION*` macros cannot be used inside a function or class.
433
434# Cardinalities #
435
436These are used in `Times()` to specify how many times a mock function will be called:
437
438|`AnyNumber()`|The function can be called any number of times.|
439|:------------|:----------------------------------------------|
440|`AtLeast(n)` |The call is expected at least `n` times.       |
441|`AtMost(n)`  |The call is expected at most `n` times.        |
442|`Between(m, n)`|The call is expected between `m` and `n` (inclusive) times.|
443|`Exactly(n) or n`|The call is expected exactly `n` times. In particular, the call should never happen when `n` is 0.|
444
445# Expectation Order #
446
447By default, the expectations can be matched in _any_ order.  If some
448or all expectations must be matched in a given order, there are two
449ways to specify it.  They can be used either independently or
450together.
451
452## The After Clause ##
453
454```
455using ::testing::Expectation;
456...
457Expectation init_x = EXPECT_CALL(foo, InitX());
458Expectation init_y = EXPECT_CALL(foo, InitY());
459EXPECT_CALL(foo, Bar())
460    .After(init_x, init_y);
461```
462says that `Bar()` can be called only after both `InitX()` and
463`InitY()` have been called.
464
465If you don't know how many pre-requisites an expectation has when you
466write it, you can use an `ExpectationSet` to collect them:
467
468```
469using ::testing::ExpectationSet;
470...
471ExpectationSet all_inits;
472for (int i = 0; i < element_count; i++) {
473  all_inits += EXPECT_CALL(foo, InitElement(i));
474}
475EXPECT_CALL(foo, Bar())
476    .After(all_inits);
477```
478says that `Bar()` can be called only after all elements have been
479initialized (but we don't care about which elements get initialized
480before the others).
481
482Modifying an `ExpectationSet` after using it in an `.After()` doesn't
483affect the meaning of the `.After()`.
484
485## Sequences ##
486
487When you have a long chain of sequential expectations, it's easier to
488specify the order using **sequences**, which don't require you to given
489each expectation in the chain a different name.  <i>All expected<br>
490calls</i> in the same sequence must occur in the order they are
491specified.
492
493```
494using ::testing::Sequence;
495Sequence s1, s2;
496...
497EXPECT_CALL(foo, Reset())
498    .InSequence(s1, s2)
499    .WillOnce(Return(true));
500EXPECT_CALL(foo, GetSize())
501    .InSequence(s1)
502    .WillOnce(Return(1));
503EXPECT_CALL(foo, Describe(A<const char*>()))
504    .InSequence(s2)
505    .WillOnce(Return("dummy"));
506```
507says that `Reset()` must be called before _both_ `GetSize()` _and_
508`Describe()`, and the latter two can occur in any order.
509
510To put many expectations in a sequence conveniently:
511```
512using ::testing::InSequence;
513{
514  InSequence dummy;
515
516  EXPECT_CALL(...)...;
517  EXPECT_CALL(...)...;
518  ...
519  EXPECT_CALL(...)...;
520}
521```
522says that all expected calls in the scope of `dummy` must occur in
523strict order. The name `dummy` is irrelevant.)
524
525# Verifying and Resetting a Mock #
526
527Google Mock will verify the expectations on a mock object when it is destructed, or you can do it earlier:
528```
529using ::testing::Mock;
530...
531// Verifies and removes the expectations on mock_obj;
532// returns true iff successful.
533Mock::VerifyAndClearExpectations(&mock_obj);
534...
535// Verifies and removes the expectations on mock_obj;
536// also removes the default actions set by ON_CALL();
537// returns true iff successful.
538Mock::VerifyAndClear(&mock_obj);
539```
540
541You can also tell Google Mock that a mock object can be leaked and doesn't
542need to be verified:
543```
544Mock::AllowLeak(&mock_obj);
545```
546
547# Mock Classes #
548
549Google Mock defines a convenient mock class template
550```
551class MockFunction<R(A1, ..., An)> {
552 public:
553  MOCK_METHODn(Call, R(A1, ..., An));
554};
555```
556See this [recipe](CookBook.md#using-check-points) for one application of it.
557
558# Flags #
559
560| `--gmock_catch_leaked_mocks=0` | Don't report leaked mock objects as failures. |
561|:-------------------------------|:----------------------------------------------|
562| `--gmock_verbose=LEVEL`        | Sets the default verbosity level (`info`, `warning`, or `error`) of Google Mock messages. |
563