Kotlin Unit-Test for combine/collect doesn't collect all items before assert

I have here two Kotlin unit-tests. The first one works, but the second doesn't. Maybe someone knows why?

This unit-test with collect on one flow works:

    @Test
    fun testEmission1() = runBlockingTest {
        val flow = MutableSharedFlow<Boolean>(replay = 1)
        val flow2 = MutableSharedFlow<Boolean>(replay = 1)
        val collectedValues = mutableListOf<Boolean>()
        val job: Job = launch {
            flow.collect {
                collectedValues.add(it)
            }
        }

        val job2 = CoroutineScope(testDispatcher).launch {
            // WORKS:
            flow2.collect {
                flow.emit(it)
            }
        }

        flow2.emit(false)
        flow2.emit(true)

        job.cancel()
        job2.cancel()

        val expectedValues = listOf(false, true)
        assertEquals(expectedValues, collectedValues)
    }

But this unit-test with combine of two flows and collect gets just the first item inside the collectedValues when it reaches the assert statement and fails:

    @Test
    fun testEmission2() = runBlockingTest {
        val flow = MutableSharedFlow<Boolean>(replay = 1)
        val flow2 = MutableSharedFlow<Boolean>(replay = 1)
        val flow3 = MutableSharedFlow<Boolean>(replay = 1)
        val collectedValues = mutableListOf<Boolean>()
        val job: Job = launch {
            flow.collect {
                collectedValues.add(it)
            }
        }

        val job2 = CoroutineScope(testDispatcher).launch {
            // doesn't work with combine/collect:
            combine(
                flow2,
                flow3,
                transform = { a, b ->
                    Pair(a, b)
                }
            ).collect {
                val (a, b) = it
                flow.emit(a)
            }
        }

        flow3.emit(false)

        flow2.emit(false)
        flow2.emit(true)

        yield() // seems to change nothing
        advanceUntilIdle() // seems to change nothing
        job.cancel()
        job2.cancel()

        val expectedValues = listOf(false, true)
        assertEquals(expectedValues, collectedValues)
    }

My testDispatcher comes from my parent class pof the unit-test:

open class BaseCoroutineTest {

    @get:Rule
    val liveDataThreadTestRule = InstantTaskExecutorRule()

    val testDispatcher = TestCoroutineDispatcher()

    @OptIn(ExperimentalCoroutinesApi::class)
    @Before
    fun replaceMainDispatcher() {
        Dispatchers.setMain(testDispatcher)
    }

    @OptIn(ExperimentalCoroutinesApi::class)
    @After
    fun resetMainDispatcher() {
        Dispatchers.resetMain()
        testDispatcher.cleanupTestCoroutines()
    }

    @After
    fun clearMocks() {
        Mockito.framework().clearInlineMocks()
    }
}

I tried to emit two values into flow2 which should trigger the collect on the combine two times. But when the unit-test reaches the assert statement there is just one item inside the collectedValues. The problem seems to be in the behaviour of the combine-function.

I'm using Kotlin 1.6.10

After trying almost a day different approaches, I found a solution.
Maybe it will be useful for someone else.

I've updated the following packages:

testImplementation "androidx.test:core:1.5.0" // from 1.4.0
testImplementation "androidx.arch.core:core-testing:2.2.0" // from 2.1.0
testImplementation "org.jetbrains.kotlinx:kotlinx-coroutines-test:1.6.1" // from 1.3.0

I changed the testDispatcher to UnconfinedTestDispatcher:

open class BaseCoroutineTest {

    @get:Rule
    val liveDataThreadTestRule = InstantTaskExecutorRule()

    val testDispatcher = UnconfinedTestDispatcher() // was: TestCoroutineDispatcher()

    @OptIn(ExperimentalCoroutinesApi::class)
    @Before
    fun replaceMainDispatcher() {
        Dispatchers.setMain(testDispatcher)
    }

    @OptIn(ExperimentalCoroutinesApi::class)
    @After
    fun resetMainDispatcher() {
        Dispatchers.resetMain()
        // testDispatcher.cleanupTestCoroutines() // commented out
    }

    @After
    fun clearMocks() {
        Mockito.framework().clearInlineMocks()
    }
}

Info: The runBlockingTest-function should be replaced after this update, because it is deprecated.