使用LiveData进行的JUnit5测试不会执行订阅者的回调

时间：2019-06-03 06:43:04

标签： android junit mockito android-livedata android-viewmodel

背景：

我有一个简单的应用程序，它使用rests API调用来获取电影列表。项目结构如下：

Activity -> ViewModel -> Repository -> ApiService (Retrofit Interface)

  1. 该活动订阅 LiveData 并监听事件更改

  2. ViewModel 托管活动观察到的 MediatorLiveData 。最初， ViewModel 在 MediatorLiveData 中设置一个Resource.loading(..)值。

  3. ViewModel 然后调用存储库以从 ApiService

    4. 获取电影列表

  4. ApiService 返回Resource.success(..)或Resource.error(..)

    5. 的 LiveData

  5. ViewModel 然后合并 MediatorLiveData

    中 ApiService 的 LiveData 结果

我的查询

在单元测试中， MediatorLiveData 仅从 ViewModel 进行第一个发射Resource.loading(..)。 MediatorLiveData 永远不会从存储库中发出任何数据。

ViewModel.class 

private var discoverMovieLiveData: MediatorLiveData<Resource<DiscoverMovieResponse>> = MediatorLiveData()

fun observeDiscoverMovie(): LiveData<Resource<DiscoverMovieResponse>> {
        return discoverMovieLiveData
    }

fun fetchDiscoverMovies(page: Int) {

        discoverMovieLiveData.value = Resource.loading(null) // this emit get observed immediately 

        val source = movieRepository.fetchDiscoverMovies(page)
        discoverMovieLiveData.addSource(source) {
            discoverMovieLiveData.value = it // never gets called
            discoverMovieLiveData.removeSource(source)
        }
    }

Repository.class 

fun fetchDiscoverMovies(page: Int): LiveData<Resource<DiscoverMovieResponse>> {
        return LiveDataReactiveStreams.fromPublisher(
            apiService.fetchDiscoverMovies(page)
                .subscribeOn(Schedulers.io())
                .map { d ->
                    Resource.success(d) // never gets called in unit test
                }
                .onErrorReturn { e ->
                    Resource.error(ApiErrorHandler.getErrorByThrowable(e), null) // // never gets called in unit test
                }
        )
    }

单元测试 

@Test
fun loadMovieListFromNetwork() {
        val mockResponse = DiscoverMovieResponse(1, emptyList(), 100, 10)
        val call: Flowable<DiscoverMovieResponse> = successCall(mockResponse) // wraps the retrofit result inside a Flowable<DiscoverMovieResponse>
        whenever(apiService.fetchDiscoverMovies(1)).thenReturn(call)

        viewModel.fetchDiscoverMovies(1)

        verify(apiService).fetchDiscoverMovies(1)
        verifyNoMoreInteractions(apiService)

        val liveData = viewModel.observeDiscoverMovie()
        val observer: Observer<Resource<DiscoverMovieResponse>> = mock()
        liveData.observeForever(observer)

        verify(observer).onChanged(
            Resource.success(mockResponse) // TEST FAILS HERE AND GETS "Resource.loading(null)" 
        )
    }

资源是一个通用包装类，用于包装不同情况下的数据，例如加载，成功，错误。

class Resource<out T>(val status: Status, val data: T?, val message: String?) {
.......
}

编辑：＃1

出于测试目的，我更新了存储库中的rx线程以在主线程上运行它。最后以 Looper not模拟异常结束。 

fun fetchDiscoverMovies(page: Int): LiveData<Resource<DiscoverMovieResponse>> {
            return LiveDataReactiveStreams.fromPublisher(
                apiService.fetchDiscoverMovies(page)
                    .subscribeOn(AndroidSchedulers.mainThread())
                    .map {...}
                    .onErrorReturn {...}
            )
        }

在测试课中，

@ExtendWith(InstantExecutorExtension::class)
class MainViewModelTest {

    companion object {
        @ClassRule
        @JvmField
        val schedulers = RxImmediateSchedulerRule()
    }

    @Test
        fun loadMovieListFromNetwork() {
        .....  
       }
}

}

RxImmediateSchedulerRule.class 

class RxImmediateSchedulerRule : TestRule {

    private val immediate = object : Scheduler() {
        override fun createWorker(): Worker {
            return ExecutorScheduler.ExecutorWorker(Executor { it.run() })
        }
    }

    override fun apply(base: Statement, description: Description): Statement {
        return object : Statement() {
            @Throws(Throwable::class)
            override fun evaluate() {
                RxJavaPlugins.setInitIoSchedulerHandler { immediate }
                RxJavaPlugins.setInitComputationSchedulerHandler { immediate }
                RxJavaPlugins.setInitNewThreadSchedulerHandler { immediate }
                RxJavaPlugins.setInitSingleSchedulerHandler { immediate }
                RxAndroidPlugins.setInitMainThreadSchedulerHandler { immediate }

                try {
                    base.evaluate()
                } finally {
                    RxJavaPlugins.reset()
                    RxAndroidPlugins.reset()
                }
            }
        }
    }

}

InstantExecutorExtension.class 

class InstantExecutorExtension : BeforeEachCallback, AfterEachCallback {

    override fun beforeEach(context: ExtensionContext?) {
        ArchTaskExecutor.getInstance().setDelegate(object : TaskExecutor() {
            override fun executeOnDiskIO(runnable: Runnable) {
                runnable.run()
            }

            override fun postToMainThread(runnable: Runnable) {
                runnable.run()
            }

            override fun isMainThread(): Boolean {
                return true
            }
        })
    }

    override fun afterEach(context: ExtensionContext?) {
        ArchTaskExecutor.getInstance().setDelegate(null)
    }

}

2 个答案:

答案 0 :(得分：2)

您指定--------------------------------------------------------------------------- UnboundLocalError Traceback (most recent call last) <ipython-input-12-360fef19693f> in <module> 1 #training the model 2 model_scratch = train(5, loaders_scratch, model_scratch, optimizer_scratch, ----> 3 criterion_scratch) <ipython-input-11-c90fddb93f0d> in train(n_epochs, loaders, model, optimizer, criterion) 9 #train model 10 model.train() ---> 11 for batch_idx, (data,target) in enumerate(loaders['train']): 12 13 # zero the parameter (weight) gradients UnboundLocalError: local variable 'photoshop' referenced before assignment 的方式不适用于JUnit5。如果您在RxImmediateSchedulerRule方法中放置一个断点，则会看到它没有被执行。

相反，您应该按照指定的here创建扩展名：

apply()

然后将 class TestSchedulerExtension : BeforeTestExecutionCallback, AfterTestExecutionCallback { override fun beforeTestExecution(context: ExtensionContext?) { RxJavaPlugins.setIoSchedulerHandler { Schedulers.trampoline() } RxJavaPlugins.setComputationSchedulerHandler { Schedulers.trampoline() } RxJavaPlugins.setNewThreadSchedulerHandler { Schedulers.trampoline() } RxAndroidPlugins.setMainThreadSchedulerHandler { Schedulers.trampoline() } } override fun afterTestExecution(context: ExtensionContext?) { RxJavaPlugins.reset() RxAndroidPlugins.reset() } } 应用于测试类的注释中，例如：

TestSchedulerExtension

现在测试将通过。现在您已经测试了，该观察者已经被分配了期望值。

从另一个角度来看：这是单元测试吗？可以肯定的是，因为在此测试中我们正在与2个单元进行交互： @ExtendWith(value = [InstantExecutorExtension::class, TestSchedulerExtension::class]) class MainViewModelTest { private val apiService: ApiService = mock() private lateinit var movieRepository: MovieRepository private lateinit var viewModel: MainViewModel @BeforeEach fun init() { movieRepository = MovieRepository(apiService) viewModel = MainViewModel(movieRepository) } @Test fun loadMovieListFromNetwork() { val mockResponse = DiscoverMovieResponse(1, emptyList(), 100, 10, 0, "", false) val call: Flowable = Flowable.just(mockResponse) whenever(apiService.fetchDiscoverMovies(1)).thenReturn(call) viewModel.fetchDiscoverMovies(1) assertEquals(Resource.success(mockResponse), LiveDataTestUtil.getValue(viewModel.discoverMovieLiveData)) } } 和MainViewModel。这更服从“集成测试”的术语。如果您嘲笑了MovieRepository，那么这将是有效的单元测试：

MoviesRepository

请注意， @ExtendWith(value = [InstantExecutorExtension::class, TestSchedulerExtension::class]) class MainViewModelTest { private val movieRepository: MovieRepository = mock() private val viewModel = MainViewModel(movieRepository) @Test fun loadMovieListFromNetwork() { val mockResponse = DiscoverMovieResponse(1, emptyList(), 100, 10, 0, "", false) val liveData = MutableLiveData>().apply { value = Resource.success(mockResponse) } whenever(movieRepository.fetchDiscoverMovies(1)).thenReturn(liveData) viewModel.fetchDiscoverMovies(1) assertEquals(Resource.success(mockResponse), getValue(viewModel.discoverMovieLiveData)) } } 应该与MovieRepository一起声明为open，以便能够对其进行模拟。另外，您可以考虑使用kotlin-allopen插件。

答案 1 :(得分：2)

我认为您要做的就是改变

val call: Flowable<DiscoverMovieResponse> = successCall(mockResponse)

到

val call: Flowable<DiscoverMovieResponse> = Flowable.just(mockResponse)

并且使用Google架构组件示例中的LiveDataUtil类。因此，您需要将其复制/粘贴到您的项目中。

因此，最终，您的新测试将如下所示（（假设在测试类的顶部正确设置了所有关联和模拟））。另外，您正在使用 InstantExecutorExtension ，就像上面的azizbekian向您显示的那样。

@Test
fun loadMovieListFromNetwork() {
    val mockResponse = DiscoverMovieResponse(1, emptyList(), 100, 10)
    val call: Flowable<DiscoverMovieResponse> = Flowable.just(mockResponse)
    whenever(apiService.fetchDiscoverMovies(1)).thenReturn(call)

    viewModel.fetchDiscoverMovies(1)

    assertEquals(Resource.success(mockResponse), LiveDataTestUtil.getValue(viewModel.discoverMovieLiveData))
}

如果该测试通过，则表明您能够成功观察到网络请求的结果并返回成功的响应。

相关问题
最新问题