I'm currently looking at some unit test librarys in C++ and have some questions:
How else would you expect something to be mockable? That's how it works in every other programming language! (Okay, not with duck typing, but that carries more overhead than virtual methods) If you're concerned about performance:
In all seriousness though, I don't think the virtual calls are going to make huge differences in performance. The one case where virtuals are bad are where they're located inside of inner loops (such as in the
iostream library where they're called possibly for every character of input or output), and even then only in performance sensitive code.
EDIT: I missed the very important word not in the above question #2 -- that you're not worried about performance. If that's the case then my answer is you're effectively screwed. A plain function or method call in C++ generates a plain method call, and there's no opprotunity for you to change where that call points. In most cases this doesn't require too much code change, because correct C++ code uses references wherever possible, which won't need to be modified despite the fact that virtuals are being used. You will have to watch out however for anyone using value semantics, because they will be subject to the slicing problem.