So I want to use mutableStateOf in my ViewModel li...

# compose

[Henning B]

So I want to use mutableStateOf in my ViewModel like this:

private var _state: State by mutableStateOf(Loading)
    override val state: State = _state

    fun onLoadClicked() {
        _state = Loading
        viewModelScope.launch {
            _state = when (val content: Content? = loadData()) {
                null -> Error
                else -> PresentData(content)
            }
        }
    }

So now I would like to test the behaviour of onLoadClicked. But I do not know how to verify that calling that function sets the state to Loading and than to PresentData/Error. I could observe a liveData and remember all states is was set to but how do I do it with mutableStateOf?

[maciejciemiega]

I think you can test it with runBlockingTest { } and use pauseDispatcher() (then it will not go through launch { } immediately, so you can test the Loading state. Then invoke advanceUntilIdle() and check the state after that.

[Henning B]

thanks, I will try that 🙏

[Henning B]

works like a charm 🙂

[Henning B]

runBlockingTest(testDispatcher) {
            pauseDispatcher()

            sut.onReloadClick()
            sut.state.shouldBeTypeOf<Loading>()

            advanceUntilIdle()
            sut.state.shouldBeTypeOf<PresentData>()
        }

[Albert Chang]

Btw you don’t need two properties. You can just write:

override var state: State by mutableStateOf(Loading)
    private set