runBlockingTest fails with "This job has not completed yet"

[PaulWoitaschek]

This simple block:

  runBlockingTest {
   suspendCancellableCoroutine<Unit> { cont ->
     thread {
       Thread.sleep(1000)
       cont.resume(Unit)
     }
   }
 }

Fails with the exception:

Exception in thread "main" java.lang.IllegalStateException: This job has not completed yet
    at kotlinx.coroutines.JobSupport.getCompletionExceptionOrNull(JobSupport.kt:1114)
    at kotlinx.coroutines.test.TestBuildersKt.runBlockingTest(TestBuilders.kt:53)
    at kotlinx.coroutines.test.TestBuildersKt.runBlockingTest$default(TestBuilders.kt:45)
    at SamplKt.main(Sampl.kt:8)
    at SamplKt.main(Sampl.kt)

This looks like a bug to me as it should pass.

Kotlin 1.3.31
Coroutines 1.2.1

[objcode]

Thank you for this minimal repro bug report!

Adding some tests for this and taking a look at getting this patched.

[objcode]

as an aside if anyone else is seeing this until it gets fixed - it appears the failure is caused by the thread (the blocking call to sleep is not required)

[objcode]

Patch #1206 should fix it!

It turns out the behavior of completion in the presence of multiple threads had a non-deterministic outcome that could, in some cases, cause a random test result.

This patch fixes the issue reported here by making it pass (as expected) while providing a detailed error message and test failure if this race condition is detected.

[rajab57]

Is there a workaround for this issue ?

[jimmymorales]

I came with this exception for some Room database tests (androidTest) using the AndroidJUnit4 runner.
It stopped throwing the exception when I added the InstantTaskExecutorRule rule.

@get:Rule
val instantExecutorRule = InstantTaskExecutorRule()

I hope this helps!

[Mugurell]

Is there a workaround for this issue ?

I'm using something like

@Test
fun test() = runBlocking {
    coroutineJob.join()
}

[Anton-Spaans-Intrepid]

@objcode I'm not sure if this patch will fix this issue entirely.

E.g. this code, that uses no other threads, fails with the "This job has not completed" message"

    runBlockingTest {
        flow<Unit> {
            suspendCancellableCoroutine<Nothing> {  }
        }.collect {  }
    }

while this code just finishes without any problems:

    runBlockingTest {
        flow<Unit> {
            delay(Long.MAX_VALUE)
        }.collect {  }
    }

[objcode]

@Anton-Spaans-Intrepid I would expect that to fail as it the collect {} will never complete.

In the patched version, you should see a 30 second wait followed by an error.

What behavior are you expecting?

[streetsofboston]

(I just discovered I used my other GitHub account ... ah well 😄)

I expect the test to never end. It will hang.