At the moment he placed the Idea in my head that i want my testsuite to run every time a file changes anyway, let someone else figure out how that is triggered. Well, someone did figure that out, thank you. It's called "PyWatch" and is a simple python script that monitors files for changes and executes a script if one has changed.

Obviously you wouldn't want to keep this going for larger code bases (the potential for overlap is horrible) but it could be quite useful when doing test-driven development to save yourself some hassle at the outset. He includes the commands you'll need to get things running and a simple PHP script that points the PyWatch instance to the correct files.