Tim Bray: "I haven't figured out how to do Test-Driven Development of concurrent systems. I know how to write tests that catch an iterator that doesn't iterate and numeric code that loses precision and a million other stupid things that every programmer does. But I don't really know how to write tests that catch simple, bone-headed, obvious errors in concurrent systems." I'd have to say that in general you can't unit test for this (in Java anyway). However there are means of alleviating matters: Understand the known patterns and idioms. Doug Lea's Java book is a fantastic source of patterns for concurrent OO. It might be the only great programming book that uses Java (great as in Dragon Book great or K&R great). Write less threaded code. Use Doug Lea's stuff, either concurrent.jar or upgrade to 1.5. There's no need to roll your own unless you're doing it for fun. Read everything Brian Goetz has to say about Java threading. Smart guy, writes well. Matt Albrecht has a nice utility in grobo utils: MultiThreadedTestRunner. Good for heightening concurrency in tests and thus flushing out bugs. Doug Schmidt's POSA2 book is a good source of patterns. It's a bit turgid in spots, but worth it for the Reactor and Half-Sync/Half-Async patterns alone. Use less threads. Events, events, events - especially for io. For valour: ExtremeProgrammingChallengeFourteen ExtremeProgrammingChallengeFourteenTheBug ConcurrencyUnitTestFinalVersion You could of course go the route of using alternative languages....
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