"Fit" is Ward Cunningham's "Framework for Integrated Tests". You can pick up a copy by starting from fit.c2.com.
I've used it for a while, and looked at some of its code along the way, but hadn't sat down and really studied it systematically. My plan is to spend an hour at a time, just digging in to what I find and sharing my notes.
1. Download and Compile
I download a copy and pull it in to my...