So this is something that has been at the back of my mind for a while. I've seen mentions of it, I've read the fitness web page and I still don't quite grok it. It seems like Fitnesse is yet another testing framework like NUnit or MbUnit or any of the others because you define inputs and outputs that you want to see but it seems to be aimed at testing the application as a whole rather than as units.
If that is so, how does it run? Do you have to design your application with hooks for fit testing? Where on the spectrum of testing does it actually fall? And can someone give me a good example of where and how fit tests could be used and what are some advantages/disadvantages?