tools/yaffs2

## gMock Cheat Sheet

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### Defining a Mock Class

#### Mocking a Normal Class {#MockClass}

Given

```cpp
class Foo {
  ...
  virtual ~Foo();
  virtual int GetSize() const = 0;
  virtual string Describe(const char* name) = 0;
  virtual string Describe(int type) = 0;
  virtual bool Process(Bar elem, int count) = 0;
};
```

(note that `~Foo()` **must** be virtual) we can define its mock as

```cpp
#include "gmock/gmock.h"

class MockFoo : public Foo {
  ...
  MOCK_METHOD(int, GetSize, (), (const, override));
  MOCK_METHOD(string, Describe, (const char* name), (override));
  MOCK_METHOD(string, Describe, (int type), (override));
  MOCK_METHOD(bool, Process, (Bar elem, int count), (override));
};
```

To create a "nice" mock, which ignores all uninteresting calls, a "naggy" mock,
which warns on all uninteresting calls, or a "strict" mock, which treats them as
failures:

```cpp
using ::testing::NiceMock;
using ::testing::NaggyMock;
using ::testing::StrictMock;

NiceMock<MockFoo> nice_foo;      // The type is a subclass of MockFoo.
NaggyMock<MockFoo> naggy_foo;    // The type is a subclass of MockFoo.
StrictMock<MockFoo> strict_foo;  // The type is a subclass of MockFoo.
```

**Note:** A mock object is currently naggy by default. We may make it nice by
default in the future.

#### Mocking a Class Template {#MockTemplate}

Class templates can be mocked just like any class.

To mock

```cpp
template <typename Elem>
class StackInterface {
  ...
  virtual ~StackInterface();
  virtual int GetSize() const = 0;
  virtual void Push(const Elem& x) = 0;
};
```

(note that all member functions that are mocked, including `~StackInterface()`
**must** be virtual).

```cpp
template <typename Elem>
class MockStack : public StackInterface<Elem> {
  ...
  MOCK_METHOD(int, GetSize, (), (const, override));
  MOCK_METHOD(void, Push, (const Elem& x), (override));
};
```

#### Specifying Calling Conventions for Mock Functions

If your mock function doesn't use the default calling convention, you can
specify it by adding `Calltype(convention)` to `MOCK_METHOD`'s 4th parameter.
For example,

```cpp
  MOCK_METHOD(bool, Foo, (int n), (Calltype(STDMETHODCALLTYPE)));
  MOCK_METHOD(int, Bar, (double x, double y),
              (const, Calltype(STDMETHODCALLTYPE)));
```

where `STDMETHODCALLTYPE` is defined by `<objbase.h>` on Windows.

### Using Mocks in Tests {#UsingMocks}

The typical work flow is:

1.  Import the gMock names you need to use. All gMock symbols are in the
    `testing` namespace unless they are macros or otherwise noted.
2.  Create the mock objects.
3.  Optionally, set the default actions of the mock objects.
4.  Set your expectations on the mock objects (How will they be called? What
    will they do?).
5.  Exercise code that uses the mock objects; if necessary, check the result
    using googletest assertions.
6.  When a mock object is destructed, gMock automatically verifies that all
    expectations on it have been satisfied.

Here's an example:

```cpp
using ::testing::Return;                          // #1

TEST(BarTest, DoesThis) {
  MockFoo foo;                                    // #2

  ON_CALL(foo, GetSize())                         // #3
      .WillByDefault(Return(1));
  // ... other default actions ...

  EXPECT_CALL(foo, Describe(5))                   // #4
      .Times(3)
      .WillRepeatedly(Return("Category 5"));
  // ... other expectations ...

  EXPECT_EQ("good", MyProductionFunction(&foo));  // #5
}                                                 // #6
```

### Setting Default Actions {#OnCall}

gMock has a **built-in default action** for any function that returns `void`,
`bool`, a numeric value, or a pointer. In C++11, it will additionally returns
the default-constructed value, if one exists for the given type.

To customize the default action for functions with return type *`T`*:

```cpp
using ::testing::DefaultValue;

// Sets the default value to be returned. T must be CopyConstructible.
DefaultValue<T>::Set(value);
// Sets a factory. Will be invoked on demand. T must be MoveConstructible.
//  T MakeT();
DefaultValue<T>::SetFactory(&MakeT);
// ... use the mocks ...
// Resets the default value.
DefaultValue<T>::Clear();
```

Example usage:

```cpp
  // Sets the default action for return type std::unique_ptr<Buzz> to
  // creating a new Buzz every time.
  DefaultValue<std::unique_ptr<Buzz>>::SetFactory(
      [] { return MakeUnique<Buzz>(AccessLevel::kInternal); });

  // When this fires, the default action of MakeBuzz() will run, which
  // will return a new Buzz object.
  EXPECT_CALL(mock_buzzer_, MakeBuzz("hello")).Times(AnyNumber());

  auto buzz1 = mock_buzzer_.MakeBuzz("hello");
  auto buzz2 = mock_buzzer_.MakeBuzz("hello");
  EXPECT_NE(nullptr, buzz1);
  EXPECT_NE(nullptr, buzz2);
  EXPECT_NE(buzz1, buzz2);

  // Resets the default action for return type std::unique_ptr<Buzz>,
  // to avoid interfere with other tests.
  DefaultValue<std::unique_ptr<Buzz>>::Clear();
```

To customize the default action for a particular method of a specific mock
object, use `ON_CALL()`. `ON_CALL()` has a similar syntax to `EXPECT_CALL()`,
but it is used for setting default behaviors (when you do not require that the
mock method is called). See [here](cook_book.md#UseOnCall) for a more detailed
discussion.

```cpp
ON_CALL(mock-object, method(matchers))
    .With(multi-argument-matcher)   ?
    .WillByDefault(action);
```

### Setting Expectations {#ExpectCall}

`EXPECT_CALL()` sets **expectations** on a mock method (How will it be called?
What will it do?):

```cpp
EXPECT_CALL(mock-object, method (matchers)?)
     .With(multi-argument-matcher)  ?
     .Times(cardinality)            ?
     .InSequence(sequences)         *
     .After(expectations)           *
     .WillOnce(action)              *
     .WillRepeatedly(action)        ?
     .RetiresOnSaturation();        ?
```

For each item above, `?` means it can be used at most once, while `*` means it
can be used any number of times.

In order to pass, `EXPECT_CALL` must be used before the calls are actually made.

The `(matchers)` is a comma-separated list of matchers that correspond to each
of the arguments of `method`, and sets the expectation only for calls of
`method` that matches all of the matchers.

If `(matchers)` is omitted, the expectation is the same as if the matchers were
set to anything matchers (for example, `(_, _, _, _)` for a four-arg method).

If `Times()` is omitted, the cardinality is assumed to be:

*   `Times(1)` when there is neither `WillOnce()` nor `WillRepeatedly()`;
*   `Times(n)` when there are `n` `WillOnce()`s but no `WillRepeatedly()`, where
    `n` >= 1; or
*   `Times(AtLeast(n))` when there are `n` `WillOnce()`s and a
    `WillRepeatedly()`, where `n` >= 0.

A method with no `EXPECT_CALL()` is free to be invoked *any number of times*,
and the default action will be taken each time.

### Matchers {#MatcherList}

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A **matcher** matches a *single* argument. You can use it inside `ON_CALL()` or
`EXPECT_CALL()`, or use it to validate a value directly using two macros:

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| Macro                                | Description                           |
| :----------------------------------- | :------------------------------------ |
| `EXPECT_THAT(actual_value, matcher)` | Asserts that `actual_value` matches `matcher`. |
| `ASSERT_THAT(actual_value, matcher)` | The same as `EXPECT_THAT(actual_value, matcher)`, except that it generates a **fatal** failure. |
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Built-in matchers (where `argument` is the function argument, e.g.
`actual_value` in the example above, or when used in the context of
`EXPECT_CALL(mock_object, method(matchers))`, the arguments of `method`) are
divided into several categories:

#### Wildcard

Matcher                     | Description
:-------------------------- | :-----------------------------------------------
`_`                         | `argument` can be any value of the correct type.
`A<type>()` or `An<type>()` | `argument` can be any value of type `type`.

#### Generic Comparison

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| Matcher                | Description                                         |
| :--------------------- | :-------------------------------------------------- |
| `Eq(value)` or `value` | `argument == value`                                 |
| `Ge(value)`            | `argument >= value`                                 |
| `Gt(value)`            | `argument > value`                                  |
| `Le(value)`            | `argument <= value`                                 |
| `Lt(value)`            | `argument < value`                                  |
| `Ne(value)`            | `argument != value`                                 |
| `IsFalse()`            | `argument` evaluates to `false` in a Boolean context. |
| `IsTrue()`             | `argument` evaluates to `true` in a Boolean context. |
| `IsNull()`             | `argument` is a `NULL` pointer (raw or smart).      |
| `NotNull()`            | `argument` is a non-null pointer (raw or smart).    |
| `Optional(m)`          | `argument` is `optional<>` that contains a value matching `m`. |
| `VariantWith<T>(m)`    | `argument` is `variant<>` that holds the alternative of type T with a value matching `m`. |
| `Ref(variable)`        | `argument` is a reference to `variable`.            |
| `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. |
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Except `Ref()`, these matchers make a *copy* of `value` in case it's modified or
destructed later. If the compiler complains that `value` doesn't have a public
copy constructor, try wrap it in `ByRef()`, e.g.
`Eq(ByRef(non_copyable_value))`. If you do that, make sure `non_copyable_value`
is not changed afterwards, or the meaning of your matcher will be changed.

#### Floating-Point Matchers {#FpMatchers}

<!-- mdformat off(no multiline tables) -->
| Matcher                          | Description                        |
| :------------------------------- | :--------------------------------- |
| `DoubleEq(a_double)`             | `argument` is a `double` value approximately equal to `a_double`, treating two NaNs as unequal. |
| `FloatEq(a_float)`               | `argument` is a `float` value approximately equal to `a_float`, treating two NaNs as unequal. |
| `NanSensitiveDoubleEq(a_double)` | `argument` is a `double` value approximately equal to `a_double`, treating two NaNs as equal. |
| `NanSensitiveFloatEq(a_float)`   | `argument` is a `float` value approximately equal to `a_float`, treating two NaNs as equal. |
| `IsNan()`   | `argument` is any floating-point type with a NaN value. |
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The above matchers use ULP-based comparison (the same as used in googletest).
They automatically pick a reasonable error bound based on the absolute value of
Mode	Name	Size
-rw-r--r--	Makefile	1037	log stats plain
d---------	patches	97	log stats plain