C++、Googlemock - 测试本地对象

Question

我开始使用 googletest 和 googlemock 库，但遇到无法解决的问题。我有这样的代码:

class Painter
{
  public:
  void DrawSomething();
};

void Painter::DrawSomething()
{
  Turtle turtle;
 turtle.doSomething();
}

main()
{
  Painter p;
  p.DrawSomething();
}

我已经模拟了 Turtle 类，但是当本地创建 turtle 对象时，我如何测试 doSomething() 方法(例如使用 EXPECT_CALL)？不修改Painter类是否可行？

感谢您的回答。

Answer 1

I have mocked the Turtle class ...

你究竟是如何 mock 它的？

... but how can I test doSomething() method (for example with EXPECT_CALL) when the object of turtle is created locally? Is it possible without modifying Painter class?
_{(Emphasis mine)}

直截了当的答案是:否。

在不通过接口(interface)解耦的情况下，您不能神奇地注入(inject)模拟而不是另一个类中使用的真实实例。

---

您应该使用类似于以下代码的内容:

struct ITurtle {
    virtual void PenUp() = 0;
    virtual void PenDown() = 0;
    virtual void TurnLeft(double degrees) = 0;
    virtual void Move(double distance) = 0;
    // ...
    virtual ~ITurtle() {}
};

---

struct TurtleMock : ITurtle {
    // Mock method declarations
    MOCK_METHOD0(PenUp, void ());
    MOCK_METHOD0(PenDown, void ());
    MOCK_METHOD1(TurnLeft, void (double));
    MOCK_METHOD1(Move, void (double));
};

---

class Turtle : public ITurtle {
public:
    void PenUp();
    void PenDown();
    void TurnLeft(double degrees);
    void Move(double distance);
};

在单独的翻译单元中为上述声明提供真正的实现。

---

class Painter {
public:
    Painter(ITurtle& turtle) : turtle_(turtle) {}   
    void DrawSomething();
private:
    ITurtle& turtle_;
};

void Painter::DrawSomething() {
    turtle_.PenDown();
    turtle_.TurnLeft(30.0);
    turtle_.Move(10.0);
    turtle_.TurnLeft(30.0);
    turtle_.Move(10.0);
    // ...
}

您也可以将 ITurtle 接口(interface)传递给 DrawSomething() 函数:

class Painter {
public:
    void DrawSomething(ITurtle& turtle);
};

void Painter::DrawSomething(ITurtle& turtle) {
    turtle.PenDown();
    turtle.TurnLeft(30.0);
    turtle.Move(10.0);
    turtle.TurnLeft(30.0);
    turtle.Move(10.0);
    // ...
}

---

int main() {
     NiceMock<TurtleMock> turtle;
     Painter p(turtle);
     // Painter p; <<< for the alternative solution

     EXPECT_CALL(turtle,PenDown())
         .Times(1);
     EXPECT_CALL(turtle,TurnLeft(_))
         .Times(2);
     EXPECT_CALL(turtle,Move(_))
         .Times(2);

     p.DrawSomething();
     //  p.DrawSomething(turtle); <<< for the alternative solution

}