How, oh how, to talk about the implementation of a tool for test-driven development? Test-drive, naturally.
The xUnit architecture comes out very smoothly in Python, so I'll switch to Python for Part II. Don't worry, I'll give a little commentary on Python, for those of you who haven't seen it before. When you're done you'll have an introduction to Python, you'll be able to write your own testing framework, and you'll have seen a trickier example of TDD—three for the price of one.