Interface Segregation Principles and Substitution Principles

You can either use abstract base classes, if that's appropriate, but most people tend to lean towards using interpaces. I guess that must tie into a lot an di no, this is kind of a controversial subject with people that are quite inter testing. But the whole mocking libraries, like m o c and n substitute, i might say, personally a big fan of mocking libraries. And certainly things where it's a function, or you just want a particular property tested, that's great. Where i tend more towards writing a concrete that just is a little bit more than a mock is.