Provided example test for withTimeout fails

[ZakTaccardi]

I just copied the following into my IDE from the README.md

@Test(expected = TimeoutCancellationException::class)
fun testFooWithTimeout() = runBlockingTest {
    val uncompleted = CompletableDeferred<Unit>() // this Deferred<Foo> will never complete
    foo(uncompleted)
    advanceTimeBy(1_000) // advance time, which will cause the timeout to throw an exception
    // ...
}

fun CoroutineScope.foo(resultDeferred: Deferred<Unit>) {
    launch {
        withTimeout(1_000) {
            resultDeferred.await() // await() will suspend forever waiting for uncompleted
            // ...
        }
    }
}

I expected the test to pass, but it failed with the following exception:

java.lang.AssertionError: Expected exception: kotlinx.coroutines.TimeoutCancellationException

	at org.junit.internal.runners.statements.ExpectException.evaluate(ExpectException.java:32)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
	at org.junit.rules.TestWatcher$1.evaluate(TestWatcher.java:55)
	at org.junit.rules.RunRules.evaluate(RunRules.java:20)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

advanceTimeBy(..) does cause the timeout exception to be thrown, but runBlockingTest may be swallowing it.

[elizarov]

cc @objcode

[douo]

Same Issue. @elizarov @objcode
pass:

    @Test(expected = Exception::class)
    fun throwException() = runBlockingTest {
        launch {
            throw Exception()
        }
    }

pass

    @Test(expected = TimeoutCancellationException::class)
    fun throwTimeoutCancellationExceptionDirectly() = runBlockingTest {
            withTimeout(-1) {}
    }

failed:

   @Test(expected = TimeoutCancellationException::class)
    fun throwTimeoutCancellationException() = runBlockingTest {
        launch {
            withTimeout(-1) {}
        }
    }

[dkhalanskyjb]

The docs are faulty here. Not much can be done on the test module's side here to make the test pass as it is, unfortunately: this issue can be replicated easily with runBlocking as well and is purely an interplay between launch and withTimeout, where the parent job doesn't cancel upon its child's failure if the exception is a CancellationException, which TimeoutCancellationException is: #1374.