Helper for ViewModel / Observable Tests

LifecycleTestOwner

import androidx.lifecycle.Lifecycle
import androidx.lifecycle.LifecycleOwner
import androidx.lifecycle.LifecycleRegistry

class LifecycleTestOwner : LifecycleOwner {

    private val registry = LifecycleRegistry(this)

    override fun getLifecycle(): Lifecycle {
        return registry
    }

    fun onCreate() {
        registry.handleLifecycleEvent(Lifecycle.Event.ON_CREATE)
    }

    fun onResume() {
        registry.handleLifecycleEvent(Lifecycle.Event.ON_RESUME)
    }

    fun onDestroy() {
        registry.handleLifecycleEvent(Lifecycle.Event.ON_DESTROY)
    }
}

MainViewModelTest

class MainViewModelTest : BaseMockitoLiveDataTest() {

    @Rule
    @JvmField
    var instantTaskExecutorRule: TestRule = InstantTaskExecutorRule()
    
    private lateinit var viewModel: MainViewModel
    private lateinit var lifecycleTestOwner: LifecycleTestOwner

    @Mock
    private lateinit var destinationObserver: Observer<Boolean>

    @Before
    fun setUp() {
        lifecycleTestOwner = LifecycleTestOwner()
        lifecycleTestOwner.onCreate()

        viewModel = MainViewModel(dependencyA)
        viewModel.destinationLiveData.observe(lifecycleTestOwner, destinationObserver)
    }

    @Test
    fun `test something`() {
        // given

        // when
        lifecycleTestOwner.onResume()
        viewModel.onStatusClicked()

        // then
        verify(destinationObserver).onChanged(true)
        
        lifecycleTestOwner.onDestroy()
    }
}