Unrelated thread can cause Awaitility to throw an exception

Awaitility sets its own UncaughtExceptionHandler globally (ConditionAwaiter:49), i.e. all spawning threads are affected. This is pretty risky and can lead to many problems, one of them being:

During an awaitility until() call, if a new thread spawns and throws an exception, the exception handler for the awaitility call catches that exception and stores it assuming the exception was caused by the awaitility callable -> the awaitility call fails (eventually even before executing the callable).

Reproducer:

@Test
public void test() {
    new Thread(() -> {
        try {
            Thread.sleep(100);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        new Thread(() -> {
            throw new RuntimeException("Some irrelevant exception");
        }).start();
    }).start();
    Awaitility.await()
        .pollDelay(500, TimeUnit.MILLISECONDS)
        .until(() -> true);
}

will fail with

java.lang.RuntimeException: Some irrelevant exception

	at com.dynatrace.oneagent.atf.common.AwaitilityReproducer.lambda$null$0(AwaitilityReproducer.java:20)
	at java.lang.Thread.run(Thread.java:748)

Tested with versions 1.7 and 3.1.2

[johanhaleby]

@dotstone May be something to reconsider now that two people have experienced issues with this in a short period of time. Thanks the feedback.

[Darkvater]

Ugh, I spent a whole day and a half tracking this down! It made it all the more tricky as things were failing from a cucumber test which does some magic with the stack trace so I would get a stack trace of a wholly unrelated exception into my cucumber steps. Anyways:

I second doing something with this. The wiki docs mentioning it are not enough, this needs a big fat warning! If I might suggest a solution: it looks like the uncaughtThroeabke is thrown in ConditionAwaiter. Is it possible to wrap it in an Awaitility exception type which:

1. At least make it clear where the exception is coming from to fail the test
2. (for bonus points) would include some description how this exception came to be and what can de done to change the behaviour (e.g. turn off)