Suppose I have a class A which depends on 3 other classes X, Y and Z, either A uses these through a reference or a pointer or say A is templated to be instantiated with X, Y and Z doesn't matter, the key is that in order to test A, I need to have X, Y and Z. So I need to have fakes for A, B and C. Suppose I write them. Now, how do I swap real and fake objects easily? I can see that this works very easily in the case of templates. In order to make it work when A depends on X, Y and Z through a reference or a pointer, I would need to have a base class say X_Interface from which I can inherit X_Real and X_Fake. So basically, I would end up in having 3 times the number of classes for every class that would need to have a fake. I am most likely missing something. There has to be a simpler way to do this. Having a base class X_Interface is also quite expensive as I will be using more space and making virtual calls. I guess I could use CRTP as I know whether its a X_Real or X_Fake at compile time but still there must be a better way.
