ConcurrentModificationException when running tests in parallel

[Michael May]

java.util.ConcurrentModificationException
java.util.Hashtable$Enumerator.next(Hashtable.java:1367)
org.testng.internal.Invoker.classConfigurationFailed(Invoker.java:430)
org.testng.internal.Invoker.confInvocationPassed(Invoker.java:455)
org.testng.internal.Invoker.invokeMethod(Invoker.java:676)
org.testng.internal.Invoker.invokeTestMethod(Invoker.java:882)
org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1189)
org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:124)
org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:108)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
java.lang.Thread.run(Thread.java:745)

I'm getting a ConcurrentModificationException every once an a while when running the test suite. Is there anyway I could prevent this? I have about 17k tests in the suite. At most one or two tests fail with this during a run, so it doesn't happen that often.

[Michael May]

hmm.. This only occurs when I synchronize the Before/After methods. After I made the blocks non-synchronized I no longer got the ConcurrentModificationException.

[Cédric Beust ♔]

Definitely a bug in TestNG but I haven't had the time to look in details.

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Cédric

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[Krishnan Mahadevan]

Michael,

Do you think you could help provide a simple test which could recreate this problem ? I can try to fix this, if there is a test that re-produces the problem.

Thanks & Regards
Krishnan Mahadevan

"All the desirable things in life are either illegal, expensive, fattening or in love with someone else!"
My Scribblings @ http://wakened-cognition.blogspot.com/

My Technical Scribbings @ http://rationaleemotions.wordpress.com/

[Cédric Beust ♔]

Also, note that ConcurrentModificationException is usually not a multithreading problem but caused by trying to iterate on a collection while an iteration is already happening (which can happen on a single thread). It doesn’t seem to be the case here, though, after a quick glance at the code (or I missed it).

​

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Cédric

[Michael May]

I'm not having that much luck on creating a test case that shows this. If I end up getting a test case together that shows this I'll post it here.