We have a similar problem at 99designs and recently open-sourced the work-distribution framework we use:<p><a href="https://github.com/99designs/testcloud" rel="nofollow">https://github.com/99designs/testcloud</a><p>The difficult part (that is not included in testcloud) is synchronizing the codebase that you are testing on the different workers. We use git and post-receive hooks to synchronize.<p>Aggregating coverage data from the distributed workers is another major TODO for us, would love to hear how Box are handling it.
This is really interesting to see how many different strategies you have to take to improve PHP unit, and impressive that many of them were very successful.