I ran across tdaemon, which automatically runs your test suite when you make a change to your source code. It is very helpful when developing. One issue I had was running the tests when tdaemon needs to monitor a huge number of files (as occurs when I have a virtualenv environment in the same directory, which has more than 100MB of code and binaries). I committed a few changes to tdaemon to allow the user to ignore any directories. For instance, if you want to ignore a virtualenv directory called "env" and the "build" and "dist" directories from distutils:

tdaemon --ignore-dirs=docs,build,env

You can even use it with any of the other tdaemon test programs, such as Django:

tdaemon --test-program=django --custom-args="myapp" --ignore-dirs=env,docs

I also uploaded tdaemon to PyPi and have tdaemon install as a script, so you don't need to keep the tdaemon.py file in your directory. Right now all the changes are on my personal fork of tdaemon on github, but hopefully will end upstream.