I am trying to test a class that is a `CoroutineSc...

# coroutines

[ziv kesten]

I am trying to test a class that is a CoroutineScope and is testing a flow emitted from a fake implementation of another class.
However, the flow does not seem to emit the data i assign it to stream.

What would you think the problem might be?

private val mainThreadSurrogate = newSingleThreadContext("UI thread")

    @Before
    fun setUp() {
        Dispatchers.setMain(mainThreadSurrogate)
    }

    @After
    fun tearDown() {
        Dispatchers.resetMain() // reset the main dispatcher to the original Main dispatcher
        mainThreadSurrogate.close()
    }

    @Test
    fun testTest(): Unit = runBlocking {
        launch(Dispatchers.Main) {
            val recorder = FakeRecordingsHandler()
            val sut = SomeClass(recorder, this.coroutineContext)
            recorder.currentTrack = flow { emit(DEMO_TRACK) }
            val isCurrentTrack = sut.isCurrentTrack(DEMO_TRACK.id)
            assertTrue(isCurrentTrack)
        }
    }
//    class SomeClass(
//        private val recorder: RecordingsHandler,
//        override val coroutineContext: CoroutineContext
//    ) : VoiceRecorder, CoroutineScope {
//
//        private var currentTrackId: String? by mutableStateOf(null)
//
//        init {
//            launch {
//                recorder.currentTrack.distinctUntilChanged().collect { demoTrack ->
//                    currentTrackId = demoTrack?.id
//            }
//         }
//
//        override fun isCurrentTrack(id: String) = currentTrackId == id
//    }

[Nick Allen]

You are collecting from currentTrack in SomeClass construction, before currentTrack is re-assigned. Try assigning first. If you want to control when the item is emitted, then you can emit into a MutableShareFlow (I'd recommend that anyways).

[ziv kesten]

Unfortunatly that does not seem to work as well, i tried with MutableSharedFlow and MutableStateFlow as well.

Also Tried using runTest { }

the init block is called but the the code inside launch block is not.

@Test
    fun testTest(): Unit = runTest {
        //launch(Dispatchers.Main) {
            val recorder = FakeRecordingsHandler()
            recorder.currentTrack = MutableStateFlow(DEMO_TRACK)
            val sut = VoiceRecorderViewModel(recorder, this.coroutineContext)
            val isCurrentTrack = sut.isCurrentTrack(DEMO_TRACK.id)
            assertTrue(isCurrentTrack)
       // }
    }

[ziv kesten]

Ok so i tried collecting using GlobalScope just to verify, and that seemed to work so i guess the problem is the coroutineScope passed to SomeClass

[Nick Allen]

The default dispatcher of runTest does not immediately run scheduled coroutine work. You'll want to call runCurrent before verifying so that the launch code inside init actually starts.