When I was doing my PhD, I once resorted to turning on all logging, printing about 60 pages of the resulting output, taping them to the floor of the lab, and crawling around on all fours with a printout of the source code tracing the execution to try and prove to myself that a result I was seeing wasn't due to just a bug in the source code. In an odd way, it's maybe my fondest memory from my dissertation work.