Sometimes you can find concurrency bugs by reading logs during concurrent execution, along with a lot of sanity checks that throw exceptions when things go wron

Sometimes you can find concurrency bugs by reading logs during concurrent execution, along with a lot of sanity checks that throw exceptions when things go wrong. You can also just look really hard at the code and simulate in your head what might go wrong. IMHO, the hardest bugs are the ones where you have too much data and/or running through the test case takes a very long amount of time. Usually the best way to chip away at these is to try and speed up the test phase by mocking things or to just do a good old stare at the code until the bug shows up. It's a cut once, measure twice approach except with time. You can either run the test again, or you can stare at the code for twice as long and not have the run the test multiple times.