One thing I am fond of is I use a little script to do the nifty rsync hard link diff backup on the directory that I am updating in, every few changes I make I save n run the script which (in the background) hard links the dir structure and creates a snapshot of the whole directory. After I am done for the day I will run my tests on the latest directory, if it fails I run the test down the list of directories until i find a pass then diff the last two directories. It makes finding core bugs that slip in very easy. The method to do the incs is
here I use a small perl script to generate a hires timestamped dirname each rotation and vim to auto run it on save. The cool thing about it is you get all of those snapshots without much disk space cause it relys on hardlinks. I know this has little to do with your question, except adhoc tests would make something like this impossible.
-Waswas