ViewModel Testing

The core-test module provides a ViewModelTest base class that sets up the testing environment for Arkitekt ViewModels.

Setup

ViewModelTest configures:

• InstantTaskExecutorRule — makes LiveData operations synchronous
• CoroutineScopeRule — sets the Main dispatcher to UnconfinedTestDispatcher for immediate coroutine execution

Basic Test

class DetailViewModelTest : ViewModelTest() {

    private lateinit var viewModel: DetailViewModel
    private lateinit var viewState: DetailViewState

    @Before
    fun setUp() {
        viewState = DetailViewState()
        viewModel = DetailViewModel(viewState)
    }

    @Test
    fun `increment number updates state`() {
        viewModel.incrementNumber()
        assertEquals(1, viewState.number.value)
    }
}

Testing Events

Use MockK's spyk to verify that events are sent:

viewModel = spyk(HomeViewModel(viewState), recordPrivateCalls = true)

viewModel.onDetail()
verify { viewModel.sendEvent(ShowDetailEvent) }

Overriding the Worker Dispatcher

By default, use cases run on Dispatchers.IO. In tests, override getWorkerDispatcher() to run everything on the Main (test) dispatcher:

every { viewModel.getWorkerDispatcher() } returns Dispatchers.Main

This ensures use case execution is synchronous and predictable in tests.