I've been doing some concurrency testing of a Java application lately. It has been slow and frustrating at times. Here are three axioms on concurrency testing that I find help me stay productive.

1) It's the how not the why. You care about how you get a system to exhibit a concurrency problem now why your test caused a concurrency problem to appear.

2) Don't rewind past the horizon. Once a concurrency problem appears measure the amount of research you do in log files and debugger traces files to a limited amount of time. For example, I know to jostle myself after 10 minutes of looking into a log file.

3) Correlate the client side activity to the server side activity. Thread pool managers, service management platforms, and user behavior impact concurrency problems. You should be using test automation in a way that will observe server-side activity to the load test activity on the client-side.

Have any axioms of your own? Please add them as a comment to this blog entry.

-Frank