Mocking C++ classes with dependency injection

Question

Say you\'re testing class A and it has a dependency injection of B which has a dependency injection of C.
So you mock B

Answer 1

In this case you should inject by pointer and not by reference, then you could pass a NULL pointer. This would work assuming you're object is indeed a mock and not a fake object, therefore it has no real dependency on the injected object.

For boost::shared_ptr you could do the following:

boost::shared_ptr null_c_ptr;
MockB mock_b(null_c_ptr);