无法在ViewModel中测试Livedata

Question

因此，我有这个ViewModel类

@HiltViewModel
class HomeViewModel @Inject constructor(private val starWarsRepository: StarWarsRepository) : ViewModel() {

    /**
     * Two-Way binding variable
     */
    val searchQuery: MutableLiveData<String> = MutableLiveData()

    val characters = searchQuery.switchMap { query ->
        if (query.isNotBlank() && query.isNotEmpty()) {
            characterPager.liveData.cachedIn(viewModelScope)
        } else {
            MutableLiveData()
        }
    }

    fun retrySearch() {
        searchQuery.postValue(searchQuery.value)
    }

    private val characterPager by lazy {
        val searchPagingConfig = PagingConfig(pageSize = 20, maxSize = 100, enablePlaceholders = false)
        Pager(config = searchPagingConfig) {
            CharacterSearchPagingSource(starWarsRepository, searchQuery.value ?: String())
        }
    }
}

，这里是反对测试频道，

@ExperimentalCoroutinesApi
@RunWith(JUnit4::class)
class HomeViewModelTest {

    @get:Rule
    val instantTaskExecutionRule = InstantTaskExecutorRule()

    private lateinit var homeViewModel: HomeViewModel
    private val starWarsAPI = mock(StarWarsAPI::class.java)
    private val testDispatcher = UnconfinedTestDispatcher()

    @Before
    fun setup() {
        Dispatchers.setMain(testDispatcher)
        homeViewModel = HomeViewModel(StarWarsRepositoryImpl(starWarsAPI, testDispatcher))
    }

    @AfterTest
    fun tearDown() {
        Dispatchers.resetMain()
    }

    @Test
    fun `live data should emit success with result when searching for a character`() = runTest {
        val character = CharacterEntity("", "", "", "172", "", listOf(), listOf())
        `when`(starWarsAPI.searchCharacters("a", null)).thenReturn(CharacterSearchResultEntity(listOf(character, character), null, null))

        homeViewModel.searchQuery.value = "a"
        val result = homeViewModel.characters.getOrAwaitValue()

        assertEquals(PagingSource.LoadResult.Page(listOf(), null, null), result)
    }
}

存储库

class StarWarsRepositoryImpl(private val starWarsAPI: StarWarsAPI, private val coroutineDispatcher: CoroutineDispatcher = Dispatchers.IO) : StarWarsRepository {

    override suspend fun searchCharacters(query: String, page: Int?) = withContext(coroutineDispatcher) {
        starWarsAPI.searchCharacters(query, page)
    }
}

这是我使用的是Google样本中的该扩展功能的

fun <T> LiveData<T>.getOrAwaitValue(time: Long = 2, timeUnit: TimeUnit = TimeUnit.SECONDS, afterObserve: () -> Unit = {}): T {
    var data: T? = null
    val latch = CountDownLatch(1)
    val observer = object : Observer<T> {
        override fun onChanged(o: T?) {
            data = o
            latch.countDown()
            [email protected](this)
        }
    }
    this.observeForever(observer)
    try {
        afterObserve.invoke()
        if (!latch.await(time, timeUnit)) {
            throw TimeoutException("LiveData value was never set.")
        }
    } finally {
        this.removeObserver(observer)
    }
    @Suppress("UNCHECKED_CAST")
    return data as T
}

。问题是我从getorawaitValue livedata值从未设置为 ？