google_mock_example.h

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

class Foo {
 public:
  virtual ~Foo() {}
  virtual char DoThis(int n) = 0;
  virtual void DoThat(const char* s, int* p) = 0;
};

class FakeFoo : public Foo {
 public:
  virtual char DoThis(int n) {
    return (n > 0) ? '+' :
        (n < 0) ? '-' : '0';
  }

  virtual void DoThat(const char* s, int* p) {
    *p = strlen(s);
  }
};

class MockFoo : public Foo {
 public:
  // Normal mock method definitions using Google Mock.
  MOCK_METHOD1(DoThis, char(int n));
  MOCK_METHOD2(DoThat, void(const char* s, int* p));

  // Delegates the default actions of the methods to a FakeFoo object.
  // This must be called *before* the custom ON_CALL() statements.
  void DelegateToFake() {
    ON_CALL(*this, DoThis(_))
        .WillByDefault(Invoke(&fake_, &FakeFoo::DoThis));
    ON_CALL(*this, DoThat(_, _))
        .WillByDefault(Invoke(&fake_, &FakeFoo::DoThat));
  }
 private:
  FakeFoo fake_;  // Keeps an instance of the fake in the mock.
};