如何在googlemock中创建部分(混合)模拟? [英] How can I create a partial (hybrid) mock in googlemock?

问题描述

Google建议

Google suggests delegating calls to a parent object when you need to invoke functionality of the real object, however this does not really create a partial (hybrid) mock. When invoking the real object, any method calls are those of the real object and not the mock object, on which you may have set up actions/expectations. How do I create a partial mock that delegates only specific methods to the real object, and all other method calls to the mock object?

using ::testing::_;
using ::testing::AtLeast;
using ::testing::Invoke;

class MockFoo : public Foo {
 public:
  MockFoo() {
    // By default, all calls are delegated to the real object.
    ON_CALL(*this, DoThis())
        .WillByDefault(Invoke(&real_, &Foo::DoThis));
    ON_CALL(*this, DoThat(_))
        .WillByDefault(Invoke(&real_, &Foo::DoThat));
    ...
  }
  MOCK_METHOD0(DoThis, ...);
  MOCK_METHOD1(DoThat, ...);
  ...
 private:
  Foo real_;
};
...

  MockFoo mock;

  EXPECT_CALL(mock, DoThis())
      .Times(3);
  EXPECT_CALL(mock, DoThat("Hi"))
      .Times(AtLeast(1));
  ... use mock in test ...

推荐答案

模拟不是将真实对象的实例创建为成员变量，而是应简单地扩展真实对象，然后默认将所有调用委托给父对象.您现在可以像平常一样设置模拟了.设置新的ON_CALL将覆盖对父级的默认调用.我们让多态性为我们完成工作-所有调用，甚至从父(真实)对象调用，都调用模拟对象，然后将ON_CALL语句设置为调用父对象或模拟行为.我们已经成功地将真实对象行为与模拟行为混合在一起.这与委派对父类的调用完全相同.. >

委托给父类示例

Instead of creating an instance of the real object as a member variable, the mock should simply extend the real object, then delegate all calls to the parent by default. You can now setup your mock like normal; setting a new ON_CALL will override the default call to the parent. We let polymorphism do the work for us -- all calls, even from the parent (real) object, invoke the mock object, then the ON_CALL statement was set to invoke either the parent object or the mock behavior. We have successfully mixed real object behavior with mock behavior. This is exactly the same as delegating calls to a parent class.

class Foo {
 public:
  virtual ~Foo();

  virtual void Pure(int n) = 0;
  virtual int Concrete(const char* str) { ... }
};

class MockFoo : public Foo {
 public:
  // Mocking a pure method.
  MOCK_METHOD1(Pure, void(int n));
  // Mocking a concrete method.  Foo::Concrete() is shadowed.
  MOCK_METHOD1(Concrete, int(const char* str));

  // Use this to call Concrete() defined in Foo.
  int FooConcrete(const char* str) { return Foo::Concrete(str); }
};

using ::testing::Invoke;
// Create mock instance foo.
...
// Delegate to parent.
ON_CALL(foo, Concrete(_))
    .WillByDefault(Invoke(&foo, &MockFoo::FooConcrete));

该技术的唯一缺点是，它需要大量样板代码并且对代码更改敏感.我扩展了googlemock来简化此过程；该代码是在此处可用.它将生成部分模拟，默认情况下会为所有方法调用父(真实)对象，并生成将参数传递给父构造函数的匹配构造函数.

The only downside to this technique is that it requires a lot of boilerplate code and is sensitive to code changes. I have extended googlemock to ease this process; the code is available here. It will generate partial mocks that call the parent (real) object by default for all methods, and generate matching constructors that pass arguments to the parent constructor.

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