How would I go about writing a test for an extremely rare race condition between two components 10 levels of indirection away covering 10s of thousands of lines of code? Because I've fixed bugs like that but can't fathom a way to write a test for it, I only even found the cause by grepping 6 months worth of logs and finding a recurring pattern.

I briefly considered writing a debugger script to pause at the right spots so QA could replicate the issue but would be a waste of everyone's time and I wouldn't want that in an automated suite.