Coroutine advanceTimeBy function doesn't work

Question

I have a simple viewModel:

class myViewModel: ViewModel() {
val someStringStateFlow = MutableStateFlow<String>("")
    fun doSomething() {
        viewModelScope.launch(DispatcherProvider.Main) {
            delay(200)
            someStringStateFlow.emit("Updated")
        }
      
    }
}

I have a test class:

class SearchViewModelTest : BehaviorSpec({

    Dispatchers.setMain(DispatcherProvider(true).Main)
    var viewModel = myViewModel()

    Given("the view model is initialized") {
        runTest {
            When("call doSomeThing") {
                viewModel.doSomething()
                advanceUntilIdle()
                advanceTimeBy(5000)
                runCurrent()
                Then("The stateflow should be updated") {
                    viewModel.someStringStateFlow.value shouldBe "Updated"
                }

            }
        }
    }

DispatcherProvider provides real or test dispatcher:

object DispatcherProvider {
    private var isTest: Boolean? = null

    operator fun invoke(isTest: Boolean? = null): DispatcherProvider {
        this.isTest = isTest
        return this
    }

    val Main: CoroutineDispatcher
        get() = getTestDispatcher(isTest) ?: Dispatchers.Main

    private fun getTestDispatcher(isTest: Boolean?): CoroutineDispatcher? =
        if (isTest == true) testDispatcher else null

    private val testDispatcher: CoroutineDispatcher by lazy {
        newSingleThreadContext("Test Dispatcher")
    }

}

This test should be successful but it fails. advanceTimeBy doesn't work correctly What is wrong here?

I'm using coroutine version 1.6.4 with the new experimental test framework

Coroutine advanceTimeBy function doesn't work

0 Answers0