Intermittent test failure - Dispatchers.Main is used concurrently with setting it

[jonalmeida]

I saw this while debugging #12143 locally:

Dispatchers.Main is used concurrently with setting it
java.lang.IllegalStateException: Dispatchers.Main is used concurrently with setting it
	at kotlinx.coroutines.test.internal.TestMainDispatcher$NonConcurrentlyModifiable.concurrentRW(TestMainDispatcher.kt:70)
	at kotlinx.coroutines.test.internal.TestMainDispatcher$NonConcurrentlyModifiable.setValue(TestMainDispatcher.kt:86)
	at kotlinx.coroutines.test.internal.TestMainDispatcher.resetDispatcher(TestMainDispatcher.kt:40)
	at kotlinx.coroutines.test.TestDispatchers.resetMain(TestDispatchers.kt:37)
	at mozilla.components.support.test.rule.MainCoroutineRule.finished(MainCoroutineRule.kt:54)
	at org.junit.rules.TestWatcher.finishedQuietly(TestWatcher.java:117)
	at org.junit.rules.TestWatcher.access$400(TestWatcher.java:46)
	at org.junit.rules.TestWatcher$1.evaluate(TestWatcher.java:64)
	at org.junit.rules.RunRules.evaluate(RunRules.java:20)
	at org.robolectric.RobolectricTestRunner$HelperTestRunner$1.evaluate(RobolectricTestRunner.java:591)
	at org.robolectric.internal.SandboxTestRunner$2.lambda$evaluate$0(SandboxTestRunner.java:274)

@Mugurell do you have any hints about this since you worked on upgrading our coroutine testing recently?

┆Issue is synchronized with this Jira Task

[Mugurell]

Not sure how a concurrent read-write may happen since we rely on JUnit callback which I expect will ensure the calls about when a test is finished and another one starts are somehow synchronized.
Thinking specifically about this maybe we should first call setMain and resetMain in MainCoroutineRule before calling super.

[jonalmeida]

Similar failures in CI too: #12227

[jonalmeida]

Similar failures in CI (PromptFeature again): #12321

[YuraLaguta]

Facing the same issue looks like the order of call won't help because the super implementations are empty

[csadilek]

Moved to bugzilla: https://bugzilla.mozilla.org/show_bug.cgi?id=1794861

Change performed by the Move to Bugzilla add-on.