Mock data member initialisation

[j2bbayle]

Hey! Just a quick question about data member initialisation for mock object: when mocking a class with data member, which get initialisation (using a constructor or in-class initialisation), it seems that the mock object does not pick up those initialised values.

A small example:

class A {
public:
    virtual void doSomething() { }
    bool getState() const { return _state; }
protected:
    bool _state = true;
};

TEST_CASE("MyTest") {
    Mock<A> Mock;
    auto mock = Mock.get();
    REQUIRE(mock.getState());  // FAILS
}

Correct me if I'm wrong, but this is not the expected behaviour, is it?

[dragospop]

It is, because you mock the interface. your mock class has no functionality except the one you specify using FakeIt. What you want is spying, and this can be done like this:

A obj;
Mock<A> spy(obj);

auto mock = spy.get();
REQUIRE(mock.getState());  // should work now

[j2bbayle]

Oh, I see. Using inheritance though, we have to stub parent members (or use spying as you pointed out), which is less straightforward:

class A {
public:
    virtual void internalUpdate() { }
    virtual void update() {
        if (_state) { internalUpdate(); }
    }
protected:
    bool _state = true;
};

class B: public A {
public:
    void internalUpdate() override {
        // do something here
    }
};

TEST_CASE("MyTest") {
    Mock<B> mockB;
    Fake(Method(mockB, internalUpdate));
    mockB.get().update();
    Verify(Method(mockB, internalUpdate)).Once();  // FAILS
}

And in this example we cannot test the correct behaviour of B without stubbing A::update() method, or make protected data member _state public.

Using spying, I cannot even handle this simple example, but I'm certainly missing something:

TEST_CASE("MyTest") {
    B anObject;
    Mock<B> spy(anObject);
    spy.get().update();
    Verify(Method(spy, internalUpdate)).Once();  // ALSO FAILS...
}