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](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.
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
112DefaultValue<T>::Set(value);  // Sets the default value to be returned.
113// ... use the mocks ...
114DefaultValue<T>::Clear();     // Resets the default value.
115```
116
117To customize the default action for a particular method, use `ON_CALL()`:
118```
119ON_CALL(mock_object, method(matchers))
120    .With(multi_argument_matcher)  ?
121    .WillByDefault(action);
122```
123
124# Setting Expectations #
125
126`EXPECT_CALL()` sets **expectations** on a mock method (How will it be
127called? What will it do?):
128```
129EXPECT_CALL(mock_object, method(matchers))
130    .With(multi_argument_matcher)  ?
131    .Times(cardinality)            ?
132    .InSequence(sequences)         *
133    .After(expectations)           *
134    .WillOnce(action)              *
135    .WillRepeatedly(action)        ?
136    .RetiresOnSaturation();        ?
137```
138
139If `Times()` is omitted, the cardinality is assumed to be:
140
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.
144
145A method with no `EXPECT_CALL()` is free to be invoked _any number of times_, and the default action will be taken each time.
146
147# Matchers #
148
149A **matcher** matches a _single_ argument.  You can use it inside
150`ON_CALL()` or `EXPECT_CALL()`, or use it to validate a value
151directly:
152
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. |
156
157Built-in matchers (where `argument` is the function argument) are
158divided into several categories:
159
160## Wildcard ##
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`.     |
164
165## Generic Comparison ##
166
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.|
178
179Except `Ref()`, these matchers make a _copy_ of `value` in case it's
180modified or destructed later. If the compiler complains that `value`
181doesn't have a public copy constructor, try wrap it in `ByRef()`,
182e.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
184matcher will be changed.
185
186## Floating-Point Matchers ##
187
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.    |
193
194The above matchers use ULP-based comparison (the same as used in
195[Google Test](http://code.google.com/p/googletest/)). They
196automatically pick a reasonable error bound based on the absolute
197value of the expected value.  `DoubleEq()` and `FloatEq()` conform to
198the IEEE standard, which requires comparing two NaNs for equality to
199return false. The `NanSensitive*` version instead treats two NaNs as
200equal, which is often what a user wants.
201
202## String Matchers ##
203
204The `argument` can be either a C string or a C++ string object:
205
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`.            |
216
217`StrCaseEq()`, `StrCaseNe()`, `StrEq()`, and `StrNe()` work for wide
218strings as well.
219
220## Container Matchers ##
221
222Most STL-style containers support `==`, so you can use
223`Eq(expected_container)` or simply `expected_container` to match a
224container exactly.   If you want to write the elements in-line,
225match them more flexibly, or get more informative messages, you can use:
226
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. |
232
233These matchers can also match:
234
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)).
237
238where the array may be multi-dimensional (i.e. its elements can be arrays).
239
240## Member Matchers ##
241
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_.|
247
248## Matching the Result of a Function or Functor ##
249
250|`ResultOf(f, m)`|`f(argument)` matches matcher `m`, where `f` is a function or functor.|
251|:---------------|:---------------------------------------------------------------------|
252
253## Pointer Matchers ##
254
255|`Pointee(m)`|`argument` (either a smart pointer or a raw pointer) points to a value that matches matcher `m`.|
256|:-----------|:-----------------------------------------------------------------------------------------------|
257
258## Multiargument Matchers ##
259
260These are matchers on tuple types. They can be used in
261`.With()`. The following can be used on functions with <i>two<br>
262arguments</i> `x` and `y`:
263
264|`Eq()`|`x == y`|
265|:-----|:-------|
266|`Ge()`|`x >= y`|
267|`Gt()`|`x > y` |
268|`Le()`|`x <= y`|
269|`Lt()`|`x < y` |
270|`Ne()`|`x != y`|
271
272You can use the following selectors to pick a subset of the arguments
273(or reorder them) to participate in the matching:
274
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))`.|
278
279## Composite Matchers ##
280
281You can make a matcher from one or more other matchers:
282
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`.               |
287
288## Adapters for Matchers ##
289
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.|
294
295## Matchers as Predicates ##
296
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`.                 |
301
302## Defining Matchers ##
303
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`]. |
308
309**Notes:**
310
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.
314
315## Matchers as Test Assertions ##
316
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`.                                                                    |
320
321# Actions #
322
323**Actions** specify what a mock function should do when invoked.
324
325## Returning a Value ##
326
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`.  |
334
335## Side Effects ##
336
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.|
346
347## Using a Function or a Functor as an Action ##
348
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.|
355
356The return value of the invoked function is used as the return value
357of the action.
358
359When defining a function or functor to be used with `Invoke*()`, you can declare any unused parameters as `Unused`:
360```
361  double Distance(Unused, double x, double y) { return sqrt(x*x + y*y); }
362  ...
363  EXPECT_CALL(mock, Foo("Hi", _, _)).WillOnce(Invoke(Distance));
364```
365
366In `InvokeArgument<N>(...)`, if an argument needs to be passed by reference, wrap it inside `ByRef()`. For example,
367```
368  InvokeArgument<2>(5, string("Hi"), ByRef(foo))
369```
370calls the mock function's #2 argument, passing to it `5` and `string("Hi")` by value, and `foo` by reference.
371
372## Default Action ##
373
374|`DoDefault()`|Do the default action (specified by `ON_CALL()` or the built-in one).|
375|:------------|:--------------------------------------------------------------------|
376
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.
378
379## Composite Actions ##
380
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.                                                                                     |
387
388## Defining Actions ##
389
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`.   |
394
395The `ACTION*` macros cannot be used inside a function or class.
396
397# Cardinalities #
398
399These are used in `Times()` to specify how many times a mock function will be called:
400
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.|
407
408# Expectation Order #
409
410By default, the expectations can be matched in _any_ order.  If some
411or all expectations must be matched in a given order, there are two
412ways to specify it.  They can be used either independently or
413together.
414
415## The After Clause ##
416
417```
418using ::testing::Expectation;
419...
420Expectation init_x = EXPECT_CALL(foo, InitX());
421Expectation init_y = EXPECT_CALL(foo, InitY());
422EXPECT_CALL(foo, Bar())
423    .After(init_x, init_y);
424```
425says that `Bar()` can be called only after both `InitX()` and
426`InitY()` have been called.
427
428If you don't know how many pre-requisites an expectation has when you
429write it, you can use an `ExpectationSet` to collect them:
430
431```
432using ::testing::ExpectationSet;
433...
434ExpectationSet all_inits;
435for (int i = 0; i < element_count; i++) {
436  all_inits += EXPECT_CALL(foo, InitElement(i));
437}
438EXPECT_CALL(foo, Bar())
439    .After(all_inits);
440```
441says that `Bar()` can be called only after all elements have been
442initialized (but we don't care about which elements get initialized
443before the others).
444
445Modifying an `ExpectationSet` after using it in an `.After()` doesn't
446affect the meaning of the `.After()`.
447
448## Sequences ##
449
450When you have a long chain of sequential expectations, it's easier to
451specify the order using **sequences**, which don't require you to given
452each expectation in the chain a different name.  <i>All expected<br>
453calls</i> in the same sequence must occur in the order they are
454specified.
455
456```
457using ::testing::Sequence;
458Sequence s1, s2;
459...
460EXPECT_CALL(foo, Reset())
461    .InSequence(s1, s2)
462    .WillOnce(Return(true));
463EXPECT_CALL(foo, GetSize())
464    .InSequence(s1)
465    .WillOnce(Return(1));
466EXPECT_CALL(foo, Describe(A<const char*>()))
467    .InSequence(s2)
468    .WillOnce(Return("dummy"));
469```
470says that `Reset()` must be called before _both_ `GetSize()` _and_
471`Describe()`, and the latter two can occur in any order.
472
473To put many expectations in a sequence conveniently:
474```
475using ::testing::InSequence;
476{
477  InSequence dummy;
478
479  EXPECT_CALL(...)...;
480  EXPECT_CALL(...)...;
481  ...
482  EXPECT_CALL(...)...;
483}
484```
485says that all expected calls in the scope of `dummy` must occur in
486strict order. The name `dummy` is irrelevant.)
487
488# Verifying and Resetting a Mock #
489
490Google Mock will verify the expectations on a mock object when it is destructed, or you can do it earlier:
491```
492using ::testing::Mock;
493...
494// Verifies and removes the expectations on mock_obj;
495// returns true iff successful.
496Mock::VerifyAndClearExpectations(&mock_obj);
497...
498// Verifies and removes the expectations on mock_obj;
499// also removes the default actions set by ON_CALL();
500// returns true iff successful.
501Mock::VerifyAndClear(&mock_obj);
502```
503
504You can also tell Google Mock that a mock object can be leaked and doesn't
505need to be verified:
506```
507Mock::AllowLeak(&mock_obj);
508```
509
510# Mock Classes #
511
512Google Mock defines a convenient mock class template
513```
514class MockFunction<R(A1, ..., An)> {
515 public:
516  MOCK_METHODn(Call, R(A1, ..., An));
517};
518```
519See this [recipe](V1_5_CookBook#Using_Check_Points.md) for one application of it.
520
521# Flags #
522
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. |