Unfortunately, if you have questions about how to write and run tests using Twisted's "trial" tool, this work in progress is still the best answer I can give you. It's a good work in progress, but it's definitely not finished.
If you need some documentation, please feel free to provide feedback and patches at
Twisted's ticket number 2443.
I am working on putting together some ramblings about test-driven
development of my own, but at this rate it's going to be quite a while until
I'm ready to post them here.