Simon is thinking about using unit testing to help with performance testing. Whilst I’ve found it useful to use unit tests as very focussed ways to run a profiler on a selection of code I don’t think it’s a good idea to tie the success of your test to it completing within a particular length of time.
After all, you might decide to run all of your tests under a tool such as Boundschecker and it would be a pity to get false failures due to the fact that the test is running slower just because you’re using some other tool or running on some other machine.
Then again, I think it could be useful to display the time it took to run the test, that way you may notice that the tests are suddenly taking longer due to a design change, or whatever…
More thought needed, I think.