使用协程对 LiveData 值进行单元测试

Question

I want to test if the viewmodel's variable has the return value of the repository call. It is my first time using Coroutines.

The problem here is that my event variable is returning null here:

Assert.assertEquals(viewModel.event.getOrAwaitValue(), EventGame(games = games))

My viewModel:

class GamesViewModel(private val repository: GameRepository) : ViewModel(), CoroutineScope {
    override val coroutineContext: CoroutineContext =
        Dispatchers.Main + SupervisorJob()

    private val _event = MutableLiveData<EventGame>()
    val event: LiveData<EventGame> get() = _event


    fun listGames() = this.launch {
        val ej = withContext(Dispatchers.Default) {
            repository.listGames()
        }
        _event.postValue(ej)
    }
}

My unit test class

class GamesUnitTest : KoinTest{
    lateinit var viewModel: GameViewModel

    private val g1 = Game(id = 1, data = "01/01/2020 18:35" ...)
    private val g2 = Game(id = 2, data = "01/10/2020 18:35"...)
    private val games = listOf(g1, g2)

    @Mock
    lateinit var repository: GameRepository

    @get:Rule
    var coroutinesTestRule = CoroutinesTestRule()

    @get:Rule
    val instantExecutorRule = InstantTaskExecutorRule()

    @Mock
    lateinit var observer: Observer<EventGame>

    @After
    fun after() {
        stopKoin()
    }

    @Before
    fun before() {
        MockitoAnnotations.initMocks(this)
        viewModel = GameViewModel(repository)
    }

    @Test
    fun testListOfGames() = runBlockingTest{
        Mockito.`when`(repository.listGames()).thenReturn(EventGame(games = games))
        viewModel.event.observeForever(observer)
        viewModel.listGames()
        Assert.assertEquals(viewModel.event.getOrAwaitValue(), EventGame(games = games))

    }
}

--Edit2

I removed the GlobalScope.launch{}. The event is still null

I'm not sure how to fix that.

Answer 1

My problem was in my Mockito. It was returning null. When I used Mockito-Kotlin it worked fine.

source: Mocked suspend function returns null in Mockito