org.junit.runners.model.InvalidTestClassError

My instrumented tests run just fine on a real devices and emulators. However, when running the tests on Firebase Test Lab I get the following error each time:

org.junit.runners.model.InvalidTestClassError: Invalid test class 'com.myapp.ui.MainInstrumentedTest':
1. No runnable methods
at org.junit.runners.ParentRunner.validate(ParentRunner.java:525)
at org.junit.runners.ParentRunner.<init>(ParentRunner.java:92)
at org.junit.runners.BlockJUnit4ClassRunner.<init>(BlockJUnit4ClassRunner.java:74)
at androidx.test.internal.runner.junit4.AndroidJUnit4ClassRunner.<init>(AndroidJUnit4ClassRunner.java:43)
at androidx.test.internal.runner.junit4.AndroidJUnit4Builder.runnerForClass(AndroidJUnit4Builder.java:65)
at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:70)
at org.junit.internal.builders.AllDefaultPossibilitiesBuilder.runnerForClass(AllDefaultPossibilitiesBuilder.java:37)
at androidx.test.internal.runner.AndroidRunnerBuilder.runnerForClass(AndroidRunnerBuilder.java:153)
at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:70)
at androidx.test.internal.runner.TestLoader.doCreateRunner(TestLoader.java:73)
at androidx.test.internal.runner.TestLoader.getRunnersFor(TestLoader.java:105)
at androidx.test.internal.runner.TestRequestBuilder.build(TestRequestBuilder.java:804)
at androidx.test.runner.AndroidJUnitRunner.buildRequest(AndroidJUnitRunner.java:575)
at androidx.test.runner.AndroidJUnitRunner.onStart(AndroidJUnitRunner.java:393)
at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:2209)

[IAmDarush]

I’ve been recently in contact with the Firebase Support team and they suggested that I try running the tests on a Physical Device instead of a Virtual Device on FTL. Following are the results:

• With coreLibraryDesugaringEnabled on, the tests failed.

• With coreLibraryDesugaringEnabled off, the tests passed.

@mannodermaus as you suggested, it appears that, desugaring with instrumentation tests on FTL has been the cause of the issue.

I’ve also reported the same results to the Firebase Support team and will report back here of any outcomes.

Thanks a lot.

[mannodermaus]

Both of you seem to execute the tests on API 29, whereas the default integration currently uses 28 - can you already tell I set this up a while ago? I’m wondering if it has something to do with the OS version. Would you mind re-running this on an API 28 device, please? I don’t have immediate resources to attend to this right away but it might be good to gather as much info as possible.

Also, @IAmDarush, that NoSuchMethodError seems to indicate you’re using core library desugaring, is that correct? It seems to look for j$.util.concurrent.ConcurrentHashMap and failing. I vaguely remember reading somewhere that desugaring & instrumentation tests on FTL don’t work together very well, but I’m unable to find this resource again.