Hi everyone :wave::skin-tone-3: I want to use a Sh...

# coroutines

[Thomas Flad]

Hi everyone 👋🏼 I want to use a SharedFlow created with the shareIn operator + WhileSubscribed to cancel/resume the SharedFlow in repeatOnLifecycle when the Android App goes to background. It’s working fine so far. I also combine this flow with a MutableStateFlow in my ViewModel to react on user input and update my state.

class MyViewModel(
    dataSource: MyDataSource,
    sharingStarted: SharingStarted = WhileSubscribed(5000)
) : ViewModel() {

    var userInput = MutableStateFlow(1)

    val state = dataSource.dataFlow()
        .combine(userInput) { data, userInput ->
            OutputClass(data, userInput)
        }
        .shareIn(viewModelScope, sharingStarted, 1)

}

My issue is that I want to test this. I’ve tried to use Turbine for this but it does not help with the combine.

@Test
fun testMyViewModel() = runBlockingTest {

    val cut = MyViewModel(
        mockk { coEvery { dataFlow() } returns flowOf(Data()) },
        sharingStarted = SharingStarted.Eagerly
    )

    cut.state.test {

        // Also an emit to the userInput here does not help
        // cut.userInput.emit(2)
        
        assertEquals(OutputClass(...), awaitItem())
    }


}

I’m getting a timeout instead of the result.

[Tgo1014]

I guess there’s some weird stuff when using Turbine with runBlockingTest

[ursus]

state vs taskListState is a typo?

[Thomas Flad]

@ursus Sorry, yes it’s a typo

[ursus]

first try runBlocking instead of runBlockingTest, second try adding doOnNext on .state flow to see if it even emits at all + printlns inside my code.. thats how I deal with this

[ursus]

also try adding userinput via the .value setter, not emit(), but yea im aware you have the default and its not necessary

[Thomas Flad]

Thanks for helping out! Using runBlocking didn’t help.

What solves the issue kind of is when I pass a scope to the ViewModel and use the TestCoroutineScope for the shareIn instead.

But then I’ll get Test finished with active jobs

[ursus]

Thats odd, all turbine does is suspend on awaitItem until the flow emits, so it shouldnt matter what scopes bla bla. If you remove the shareIn sharing, does it work?

[Thomas Flad]

Without the shareIn the tests are working fine (with Turbine).

What I don’t understand is that the test is working when I don’t combine with the MutableStateFlow. I can test the shareIn without the combine

[expensivebelly]

So it’s either testing combine or shareIn but not both?

[Nick Allen]

Never used Turbine but docs suggest to me that you are missing cancelAndConsumeRemainingEvents() at end of test block. test doesn't return until Flow is complete or cancelled. The result of shareIn never completes so you need to cancel it. https://github.com/cashapp/turbine#hot-flows