ExampleViewModel.kt

class ExampleViewModel(private val logger: Logger) : ViewModel() {

    @VisibleForTesting
    var job: Job? = null

    fun handleError() {
        job = viewModelScope.launch(Dispatchers.IO) {
            heavyOperation()
            logger.logErrorEvent()
        }
    }
    
}

ExampleViewModelTest.kt

class ExampleViewModelTest {

    private val logger: Logger = mock()
    private val testee: ExampleViewModel = ExampleViewModel(logger)

    @Test
    fun test() = runBlocking {
        testee.handleError()
        testee.job?.join()
        verify(logger).logErrorEvent()
    }
}

Test passes