242 lines
7.2 KiB
Markdown
242 lines
7.2 KiB
Markdown
# gMock Cheat Sheet
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## Defining a Mock Class
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### Mocking a Normal Class {#MockClass}
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Given
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```cpp
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class Foo {
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...
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virtual ~Foo();
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virtual int GetSize() const = 0;
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virtual string Describe(const char* name) = 0;
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virtual string Describe(int type) = 0;
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virtual bool Process(Bar elem, int count) = 0;
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};
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```
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(note that `~Foo()` **must** be virtual) we can define its mock as
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```cpp
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#include "gmock/gmock.h"
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class MockFoo : public Foo {
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...
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MOCK_METHOD(int, GetSize, (), (const, override));
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MOCK_METHOD(string, Describe, (const char* name), (override));
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MOCK_METHOD(string, Describe, (int type), (override));
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MOCK_METHOD(bool, Process, (Bar elem, int count), (override));
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};
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```
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To create a "nice" mock, which ignores all uninteresting calls, a "naggy" mock,
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which warns on all uninteresting calls, or a "strict" mock, which treats them as
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failures:
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```cpp
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using ::testing::NiceMock;
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using ::testing::NaggyMock;
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using ::testing::StrictMock;
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NiceMock<MockFoo> nice_foo; // The type is a subclass of MockFoo.
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NaggyMock<MockFoo> naggy_foo; // The type is a subclass of MockFoo.
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StrictMock<MockFoo> strict_foo; // The type is a subclass of MockFoo.
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```
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{: .callout .note}
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**Note:** A mock object is currently naggy by default. We may make it nice by
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default in the future.
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### Mocking a Class Template {#MockTemplate}
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Class templates can be mocked just like any class.
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To mock
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```cpp
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template <typename Elem>
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class StackInterface {
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...
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virtual ~StackInterface();
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virtual int GetSize() const = 0;
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virtual void Push(const Elem& x) = 0;
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};
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```
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(note that all member functions that are mocked, including `~StackInterface()`
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**must** be virtual).
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```cpp
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template <typename Elem>
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class MockStack : public StackInterface<Elem> {
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...
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MOCK_METHOD(int, GetSize, (), (const, override));
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MOCK_METHOD(void, Push, (const Elem& x), (override));
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};
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```
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### Specifying Calling Conventions for Mock Functions
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If your mock function doesn't use the default calling convention, you can
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specify it by adding `Calltype(convention)` to `MOCK_METHOD`'s 4th parameter.
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For example,
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```cpp
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MOCK_METHOD(bool, Foo, (int n), (Calltype(STDMETHODCALLTYPE)));
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MOCK_METHOD(int, Bar, (double x, double y),
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(const, Calltype(STDMETHODCALLTYPE)));
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```
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where `STDMETHODCALLTYPE` is defined by `<objbase.h>` on Windows.
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## Using Mocks in Tests {#UsingMocks}
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The typical work flow is:
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1. Import the gMock names you need to use. All gMock symbols are in the
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`testing` namespace unless they are macros or otherwise noted.
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2. Create the mock objects.
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3. Optionally, set the default actions of the mock objects.
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4. Set your expectations on the mock objects (How will they be called? What
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will they do?).
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5. Exercise code that uses the mock objects; if necessary, check the result
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using googletest assertions.
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6. When a mock object is destructed, gMock automatically verifies that all
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expectations on it have been satisfied.
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Here's an example:
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```cpp
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using ::testing::Return; // #1
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TEST(BarTest, DoesThis) {
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MockFoo foo; // #2
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ON_CALL(foo, GetSize()) // #3
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.WillByDefault(Return(1));
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// ... other default actions ...
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EXPECT_CALL(foo, Describe(5)) // #4
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.Times(3)
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.WillRepeatedly(Return("Category 5"));
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// ... other expectations ...
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EXPECT_EQ(MyProductionFunction(&foo), "good"); // #5
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} // #6
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```
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## Setting Default Actions {#OnCall}
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gMock has a **built-in default action** for any function that returns `void`,
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`bool`, a numeric value, or a pointer. In C++11, it will additionally returns
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the default-constructed value, if one exists for the given type.
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To customize the default action for functions with return type `T`, use
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[`DefaultValue<T>`](reference/mocking.md#DefaultValue). For example:
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```cpp
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// Sets the default action for return type std::unique_ptr<Buzz> to
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// creating a new Buzz every time.
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DefaultValue<std::unique_ptr<Buzz>>::SetFactory(
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[] { return MakeUnique<Buzz>(AccessLevel::kInternal); });
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// When this fires, the default action of MakeBuzz() will run, which
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// will return a new Buzz object.
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EXPECT_CALL(mock_buzzer_, MakeBuzz("hello")).Times(AnyNumber());
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auto buzz1 = mock_buzzer_.MakeBuzz("hello");
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auto buzz2 = mock_buzzer_.MakeBuzz("hello");
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EXPECT_NE(buzz1, nullptr);
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EXPECT_NE(buzz2, nullptr);
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EXPECT_NE(buzz1, buzz2);
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// Resets the default action for return type std::unique_ptr<Buzz>,
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// to avoid interfere with other tests.
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DefaultValue<std::unique_ptr<Buzz>>::Clear();
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```
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To customize the default action for a particular method of a specific mock
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object, use [`ON_CALL`](reference/mocking.md#ON_CALL). `ON_CALL` has a similar
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syntax to `EXPECT_CALL`, but it is used for setting default behaviors when you
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do not require that the mock method is called. See
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[Knowing When to Expect](gmock_cook_book.md#UseOnCall) for a more detailed
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discussion.
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## Setting Expectations {#ExpectCall}
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See [`EXPECT_CALL`](reference/mocking.md#EXPECT_CALL) in the Mocking Reference.
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## Matchers {#MatcherList}
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See the [Matchers Reference](reference/matchers.md).
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## Actions {#ActionList}
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See the [Actions Reference](reference/actions.md).
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## Cardinalities {#CardinalityList}
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See the [`Times` clause](reference/mocking.md#EXPECT_CALL.Times) of
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`EXPECT_CALL` in the Mocking Reference.
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## Expectation Order
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By default, expectations can be matched in *any* order. If some or all
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expectations must be matched in a given order, you can use the
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[`After` clause](reference/mocking.md#EXPECT_CALL.After) or
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[`InSequence` clause](reference/mocking.md#EXPECT_CALL.InSequence) of
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`EXPECT_CALL`, or use an [`InSequence` object](reference/mocking.md#InSequence).
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## Verifying and Resetting a Mock
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gMock will verify the expectations on a mock object when it is destructed, or
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you can do it earlier:
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```cpp
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using ::testing::Mock;
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...
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// Verifies and removes the expectations on mock_obj;
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// returns true if and only if successful.
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Mock::VerifyAndClearExpectations(&mock_obj);
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...
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// Verifies and removes the expectations on mock_obj;
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// also removes the default actions set by ON_CALL();
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// returns true if and only if successful.
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Mock::VerifyAndClear(&mock_obj);
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```
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Do not set new expectations after verifying and clearing a mock after its use.
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Setting expectations after code that exercises the mock has undefined behavior.
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See [Using Mocks in Tests](gmock_for_dummies.md#using-mocks-in-tests) for more
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information.
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You can also tell gMock that a mock object can be leaked and doesn't need to be
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verified:
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```cpp
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Mock::AllowLeak(&mock_obj);
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```
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## Mock Classes
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gMock defines a convenient mock class template
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```cpp
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class MockFunction<R(A1, ..., An)> {
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public:
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MOCK_METHOD(R, Call, (A1, ..., An));
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};
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```
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See this [recipe](gmock_cook_book.md#using-check-points) for one application of
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it.
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## Flags
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| Flag | Description |
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| :----------------------------- | :---------------------------------------- |
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| `--gmock_catch_leaked_mocks=0` | Don't report leaked mock objects as failures. |
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| `--gmock_verbose=LEVEL` | Sets the default verbosity level (`info`, `warning`, or `error`) of Google Mock messages. |
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