mock object to return a real object with same arguments

Question

I'm trying to mock a factory. In this example, this factory has a method create which takes two args and return a C object with has a constructor which takes same two args. I'd like to setup my factory to when I order my factory to create a new C, it returns a real new C with given args to create method.

Mockito.when(myFactory.create(Mockito.any(A.class), Mockito.any(B.class)))
    .thenReturn(new C(??, ??));

How can I achieve this? Any help will be appreciated

Answer 1

Use doAnswer to capture and use the parameters passed to the mocked factory call.

For example:

MyFactory myFactory = mock(MyFactory.class);

Answer<C> answer = new Answer<C>() {
    public C answer(InvocationOnMock invocation) throws Throwable {
        A a = invocation.getArgument(0, A.class);
        B b = invocation.getArgument(1, B.class);
        return new C(a, b);
    }
};

// either of these ...
when(myFactory.create(Mockito.any(A.class), Mockito.any(B.class))).thenAnswer(answer);

doAnswer(answer).when(myFactory.create(Mockito.any(A.class), Mockito.any(B.class)));

Answer 2

Try this:

MyFactory myFactory = mock(MyFactory.class);
A a = new A();
B b = new B();
doReturn(new C(a, b)).when(myFactory).create(eq(a), eq(b));

Just import eq method from hamcrest.