使用 Repository + LiveData + Coroutines 进行 ViewModel 单元测试

Question

所以我对如何对我的 ViewModel 实施单元测试感到困惑。 我正在使用 retrofit 来获取和使用存储库的 API。

视图模型.kt

@HiltViewModel
class MoviesViewModel @Inject constructor(private val moviesRepository: MoviesRepository) :
ViewModel() {
private val _navigatetoDetail = MutableLiveData<Movies?>()

fun getPopularMovies() = liveData(Dispatchers.Default) {
    emit(Resource.loading(null))
    try {
        emit(Resource.success(moviesRepository.getPopularMovies()))
    } catch (e: Exception) {
        emit(
            Resource.error(
                null,
                e.message ?: "Unknown Error"
            )
        )
        Log.e("viewModel", "popularMovies error: ${e.message}")
    }
}

fun getMovieDetails(movie_id: String) = liveData(Dispatchers.Default) {
    emit(Resource.loading(null))
    try {
        emit(Resource.success(moviesRepository.getMovieDetails(movie_id)))
    } catch (e: Exception) {
        emit(
            Resource.error(
                null,
                e.message ?: "Unknown Error"
            )
        )
        Log.e("viewModel", "movieDetails error: ${e.message}")
    }
}

fun navigatetoDetail(): LiveData<Movies?> {
    return _navigatetoDetail
}

fun onMovieClicked(movies: Movies?) {
    _navigatetoDetail.value = movies
}

fun onMovieDetailNavigated() {
    _navigatetoDetail.value = null
}

存储库.kt

class MoviesRepository @Inject constructor(private var apiInterface: ApiInterface) {
init {
    apiInterface = ApiBuilder.createService()
}

suspend fun getPopularMovies() = apiInterface.getPopularMovies()

suspend fun getMovieDetails(movie_id: String) = apiInterface.getMovieDetails(movie_id)

suspend fun getPopularTvShows() = apiInterface.getPopularTvShows()

suspend fun getTvShowDetails(tvshow_id: String) = apiInterface.getTvShowDetails(tvshow_id)

api接口.kt

interface ApiInterface {
@GET("/3/movie/popular?api_key=$API_KEY&language=en-US")
suspend fun getPopularMovies(): Envelope<List<Movies>>

@GET("/3/movie/{movie_id}?api_key=$API_KEY&language=en-US")
suspend fun getMovieDetails(@Path("movie_id") movie_id: String?): Movies

@GET("3/tv/popular?api_key=$API_KEY&language=en-US&page=1")
suspend fun getPopularTvShows(): Envelope<List<TvShows>>

@GET("/3/tv/{tvshow_id}?api_key=$API_KEY&language=en-US")
suspend fun getTvShowDetails(@Path("tvshow_id") tvshow_id: String?): TvShows

我已经尝试通过如下方式测试我的 ViewModel：

 @Test
fun testGetPopularMovies() = coroutinesTestRule.testDispatcher.runBlockingTest {
    val moviesList = viewModel.getPopularMovies().value
    viewModel.getPopularMovies().observeForever(observer)
    verify(observer).onChanged(argumentCaptor.capture())
    assertEquals(20, moviesList?.data?.results?.size)
}

但它在viewModel.getPopularMovies().observeForever(observer)上返回 NullPointerException

Answer 1

这是一个扩展 function 用于等待实时数据结果。 在您的测试 package 下使用以下代码创建 koltin 扩展 function。

import androidx.annotation.VisibleForTesting
import androidx.lifecycle.LiveData
import androidx.lifecycle.Observer
import java.util.concurrent.CountDownLatch
import java.util.concurrent.TimeUnit
import java.util.concurrent.TimeoutException


@VisibleForTesting(otherwise = VisibleForTesting.NONE)
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()
        this@getOrAwaitValue.removeObserver(this)
    }
}
this.observeForever(observer)

try {
    afterObserve.invoke()

    // Don't wait indefinitely if the LiveData is not set.
    if (!latch.await(time, timeUnit)) {
        throw TimeoutException("LiveData value was never set.")
    }

} finally {
    this.removeObserver(observer)
}

@Suppress("UNCHECKED_CAST")
return data as T
}

这是示例视图 model class 测试。LoginViewmodel class 扩展了 AndroidViewModel 而不是 ViewModel。

import androidx.arch.core.executor.testing.InstantTaskExecutorRule
import androidx.test.core.app.ApplicationProvider
import androidx.test.ext.junit.runners.AndroidJUnit4
import com.mymaskreminder.ui.getOrAwaitValue
import org.junit.Assert
import org.junit.Rule
import org.junit.Test
import org.junit.runner.RunWith

@RunWith(AndroidJUnit4::class)
class LoginViewModelTest {

@get:Rule
var instantExecutorRule = InstantTaskExecutorRule()


@Test
fun sendLoginRequest() {


    val loginViewModel = LoginViewModel(ApplicationProvider.getApplicationContext())


    loginViewModel.sendLoginRequest("test@gmail.com", "12345")

    //shadowOf(Looper.getMainLooper()).idle()


    val value_error = loginViewModel.loginErrorResponse.getOrAwaitValue()


    Assert.assertEquals(value_error.toString(),
        "Unauthorized !"
    )



}
}

Answer 2

您需要有一个 testCoroutineDispatcher 或 testCoroutineScope 才能将您的 viewModel 的 scope 设置为测试的 scope。 添加此 class：

@ExperimentalCoroutinesApi
class CoroutineTestRule : TestWatcher(), TestCoroutineScope by TestCoroutineScope() {

override fun starting(description: Description) {
    super.starting(description)
    Dispatchers.setMain(this.coroutineContext[ContinuationInterceptor] as CoroutineDispatcher)
}

override fun finished(description: Description) {
    super.finished(description)
    Dispatchers.resetMain()
}

}

并用于测试 class：

@SmallTest
@RunWith(PowerMockRunner::class)
class BaseRepositoryTest {

    @get:Rule
    var instantTaskExecutorRule = InstantTaskExecutorRule()

    @get:Rule
    var coroutineTestRule = CoroutineTestRule()

}

不要忘记将 runBlockingTest 用于测试功能。 coroutinesTest 库上可用的 runBlockingTest：

testImplementation("org.jetbrains.kotlinx:kotlinx-coroutines-test:1.4.3")

 @Test
    fun `success user login`() {
        runBlockingTest {
            viewModel.sendLoginRequest(PHONE_VALID_NUMBER1)
            val result = viewModel.liveData.getOrAwaitValueTest()
            assert(result == LoginViewModel.Views(PHONE_VALID_NUMBER1))

        }
    }

也使用 getOrAwaitValue 来观察 api 结果