"Performance Testing with JUnitPerf" article
Andrew Glover, who has been publishing a series of articles related to code quality on IBM developerWorks, talks about "Peformance Testing with JUnitPerf". The idea is to decorate your unit tests with timing constraints, so that they also become performance tests. If you want to do the same in Python, I happen to know about pyUnitPerf, the Python port of JUnitPerf. Here is a blog post/tutorial I wrote a while ago on pyUnitPerf.