am writing tests for my `ViewModel` that exposes state with `StateFlow`. I want to test that it emit...

# android

[Marko Novakovic]

am writing tests for my ViewModel that exposes state with StateFlow. I want to test that it emits Loading state and than starting data fetching process from init block. when I provide fake API I can’t catch Loading state because data is fetched immediately and Success state is emitted. how to test that Loading comes first followed by Success?

[Adam Powell]

Provide a fake that doesn't complete until you tell the fake to complete, then you can check for loading, advance the fake, then check that the loaded data is available

[Marko Novakovic]

can you maybe link to some example for this?

[Scott Kruse]

Usually i'll do something like this

val stateList: MutableList<UiState> = mutableListOf()

            val job = launch {
                uiStateFlow.toList(stateList)
            }

            // do thing under test
            
            stateList.size shouldEqual 2
            stateList.first() shouldEqual Loading
            stateList[1] shouldEqual Success

[Marko Novakovic]

this runs forever

[Marko Novakovic]

and where exactly should I call toList()

[Francesc]

It runs forever because you need to cancel the job after doing the thing under test

[Marko Novakovic]

thanks everyone

[Damian Zawadzki]

For testing flows use turbine
https://github.com/cashapp/turbine