ViewModelTest.kt

class FlowViewModelTest {

    @get:Rule
    val rule = MainCoroutineRule()

    private companion object {
        val CHARACTERS = listOf('A', 'B', 'C')
    }

    private val repository = mock<CharacterRepository>().apply {
        whenever(getCharacters()).thenReturn(flowOf(CHARACTERS))
    }
    private lateinit var viewModel: FlowViewModel
    private lateinit var stateObserver: TestObserver<State>
    
    @Test
    fun `should load characters on subscribe`(){
        rule.setup {
            viewModel = FlowViewModel(repository)
            stateObserver = viewModel.state.test()
        }

        rule.run {
            stateObserver.assertValues(
                State(isLoading = false, characters = emptyList()),
                State(isLoading = true, characters = emptyList()),
                State(isLoading = false, characters = CHARACTERS)
            )
        }
    }
    
}