问题

Question

问题

使用Kotlin协程为Android单元测试注入viewModelScope的最佳策略是什么？
将CoroutineScope注入ViewModel进行单元测试时，即使在生产代码中不需要，也应该使用flowOn注入和定义CoroutineDispatcher吗？

在此用例中，生产代码中不需要

flowOn，因为Retrofit在 SomeRepository.kt 中处理Dispatchers.IO上的线程，并且viewModelScope返回默认情况下，Dispathers.Main上的数据。

预期

对保存在Kotlin Flow值中的Android ViewModel视图状态值进行单元测试。

已观察

具有主调度程序的模块无法初始化。对于测试，可以使用kotlinx-coroutines-test模块中的Dispatchers.setMain

在第一次对CoroutineScope进行硬编码的情况下，单元测试失败。使用viewModelScope以便启动的协程将维持ViewModel的生命周期。但是，viewModelScope是在ViewModel内部创建的，与可在ViewModel外部定义并作为参数传递的CoroutineDispatcher相比，它的注入更加复杂。

实施

SomeViewModel.kt

fun bindIntents(view: FeedView) {
    view.initStateIntent().onEach {
        initState(view)
    }.launchIn(viewModelScope)        
}

SomeTest.kt

@ExperimentalCoroutinesApi
class SomeTest : BeforeAllCallback, AfterAllCallback {

    private val testDispatcher = TestCoroutineDispatcher()
    private val testScope = TestCoroutineScope(testDispatcher)
    private val repository = mockkClass(FeedRepository::class)
    private var loadNetworkIntent = MutableStateFlow<LoadNetworkIntent?>(null)

    override fun beforeAll(context: ExtensionContext?) {
        // Set Coroutine Dispatcher.
        Dispatchers.setMain(testDispatcher)
    }

    override fun afterAll(context: ExtensionContext?) {
        Dispatchers.resetMain()
        // Reset Coroutine Dispatcher and Scope.
        testDispatcher.cleanupTestCoroutines()
        testScope.cleanupTestCoroutines()
    }

    @Test
    fun topCafesPoc() = testDispatcher.runBlockingTest {
        coEvery {
            repository.getInitialCafes(any())
        } returns mockGetInitialCafes(mockCafesList, SUCCESS)

        val viewModel = FeedViewModel(repository)
        viewModel.bindIntents(object : FeedView {
            @ExperimentalCoroutinesApi
            override fun initStateIntent() = MutableStateFlow(true)

            @ExperimentalCoroutinesApi
            override fun loadNetworkIntent() = loadNetworkIntent.filterNotNull()

            override fun render(viewState: FeedViewState) {
                // TODO: Test viewState
            }

        })
        loadNetworkIntent.value = LoadNetworkIntent(true)
        // TODO
        // assertEquals(4, 2 + 2)
    }
}

注意：最终版本将使用JUnit 5测试扩展。

完整错误日志

线程“ main @ coroutine＃1”中的异常java.lang.IllegalStateException：具有主调度程序的模块无法初始化。对于测试，可以使用kotlinx-coroutines-test模块中的Dispatchers.setMain 在kotlinx.coroutines.internal.MissingMainCoroutineDispatcher.missing（MainDispatchers.kt：113）在kotlinx.coroutines.internal.MissingMainCoroutineDispatcher.isDispatchNeeded（MainDispatchers.kt：91）在kotlinx.coroutines.DispatchedContinuationKt.resumeCancellableWith（DispatchedContinuation.kt：285）在kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable（Cancellable.kt：26）在kotlinx.coroutines.CoroutineStart.invoke（CoroutineStart.kt：109）在kotlinx.coroutines.AbstractCoroutine.start（AbstractCoroutine.kt：158）在kotlinx.coroutines.BuildersKt__Builders_commonKt.launch（Builders.common.kt：56）在kotlinx.coroutines.BuildersKt.launch（来源不明）在kotlinx.coroutines.BuildersKt__Builders_commonKt.launch $ default（Builders.common.kt：49）在kotlinx.coroutines.BuildersKt.launch $ default（未知来源）在kotlinx.coroutines.flow.FlowKt__CollectKt.launchIn（Collect.kt：49）在kotlinx.coroutines.flow.FlowKt.launchIn（未知来源）在app.topcafes.feed.viewmodel.FeedViewModel.bindIntents（FeedViewModel.kt：38）在app.topcafes.FeedTest $ topCafesPoc $ 1.invokeSuspend（FeedTest.kt：53）在app.topcafes.FeedTest $ topCafesPoc $ 1.invoke（FeedTest.kt）在kotlinx.coroutines.test.TestBuildersKt $ runBlockingTest $ deferred $ 1.invokeSuspend（TestBuilders.kt：50）在kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith（ContinuationImpl.kt：33）在kotlinx.coroutines.DispatchedTask.run（DispatchedTask.kt：56）在kotlinx.coroutines.test.TestCoroutineDispatcher.dispatch（TestCoroutineDispatcher.kt：50）在kotlinx.coroutines.DispatchedContinuationKt.resumeCancellableWith（DispatchedContinuation.kt：288）在kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable（Cancellable.kt：26）在kotlinx.coroutines.CoroutineStart.invoke（CoroutineStart.kt：109）在kotlinx.coroutines.AbstractCoroutine.start（AbstractCoroutine.kt：158）在kotlinx.coroutines.BuildersKt__Builders_commonKt.async（Builders.common.kt：91）在kotlinx.coroutines.BuildersKt.async（未知来源）在kotlinx.coroutines.BuildersKt__Builders_commonKt.async $ default（Builders.common.kt：84）在kotlinx.coroutines.BuildersKt.async $ default（未知来源）在kotlinx.coroutines.test.TestBuildersKt.runBlockingTest（TestBuilders.kt：49）在kotlinx.coroutines.test.TestBuildersKt.runBlockingTest（TestBuilders.kt：80）在app.topcafes.FeedTest.topCafesPoc（FeedTest.kt：47）在sun.reflect.NativeMethodAccessorImpl.invoke0（本机方法）处在sun.reflect.NativeMethodAccessorImpl.invoke（NativeMethodAccessorImpl.java:62）在sun.reflect.DelegatingMethodAccessorImpl.invoke（DelegatingMethodAccessorImpl.java:43）在java.lang.reflect.Method.invoke（Method.java:498）在org.junit.runners.model.FrameworkMethod $ 1.runReflectiveCall（FrameworkMethod.java:50）在org.junit.internal.runners.model.ReflectiveCallable.run（ReflectiveCallable.java:12）在org.junit.runners.model.FrameworkMethod.invokeExplosively（FrameworkMethod.java:47）在org.junit.internal.runners.statements.InvokeMethod.evaluate（InvokeMethod.java:17）在org.junit.runners.ParentRunner.runLeaf（ParentRunner.java:325）在org.junit.runners.BlockJUnit4ClassRunner.runChild（BlockJUnit4ClassRunner.java:78）在org.junit.runners.BlockJUnit4ClassRunner.runChild（BlockJUnit4ClassRunner.java:57）在org.junit.runners.ParentRunner $ 3.run（ParentRunner.java:290）在org.junit.runners.ParentRunner上$ 1.schedule（ParentRunner.java:71）在org.junit.runners.ParentRunner.runChildren（ParentRunner.java:288）在org.junit.runners.ParentRunner.access $ 000（ParentRunner.java:58）在org.junit.runners.ParentRunner上$ 2.evaluate（ParentRunner.java:268）在org.junit.runners.ParentRunner.run（ParentRunner.java:363）在org.junit.runner.JUnitCore.run（JUnitCore.java:137）在com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs（JUnit4IdeaTestRunner.java:68）在com.intellij.rt.junit.IdeaTestRunner $ Repeater.startRunnerWithArgs（IdeaTestRunner.java:33）在com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart（JUnitStarter.java:230）在com.intellij.rt.junit.JUnitStarter.main（JUnitStarter.java:58）由以下原因引起：java.lang.RuntimeException：android.os.Looper中的方法getMainLooper没有被模拟。有关详情，请参见http://g.co/androidstudio/not-mocked。在android.os.Looper.getMainLooper（Looper.java）在kotlinx.coroutines.android.AndroidDispatcherFactory.createDispatcher（HandlerDispatcher.kt：55）在kotlinx.coroutines.android.AndroidDispatcherFactory.createDispatcher（HandlerDispatcher.kt：52）在kotlinx.coroutines.internal.MainDispatchersKt.tryCreateDispatcher（MainDispatchers.kt：57）在kotlinx.coroutines.test.internal.TestMainDispatcher.getDelegate（MainTestDispatcher.kt：19）在kotlinx.coroutines.test.internal.TestMainDispatcher.getImmediate（MainTestDispatcher.kt：32）在androidx.lifecycle.ViewModelKt.getViewModelScope（ViewModel.kt：42） ...另外40个线程“主@ coroutine＃1”中的异常java.lang.IllegalStateException：具有主调度程序的模块无法初始化。对于测试，可以使用kotlinx-coroutines-test模块中的Dispatchers.setMain 在kotlinx.coroutines.internal.MissingMainCoroutineDispatcher.missing（MainDispatchers.kt：113）在kotlinx.coroutines.internal.MissingMainCoroutineDispatcher.isDispatchNeeded（MainDispatchers.kt：91）在kotlinx.coroutines.DispatchedContinuationKt.resumeCancellableWith（DispatchedContinuation.kt：285）在kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable（Cancellable.kt：26）在kotlinx.coroutines.CoroutineStart.invoke（CoroutineStart.kt：109）在kotlinx.coroutines.AbstractCoroutine.start（AbstractCoroutine.kt：158）在kotlinx.coroutines.BuildersKt__Builders_commonKt.launch（Builders.common.kt：56）在kotlinx.coroutines.BuildersKt.launch（来源不明）在kotlinx.coroutines.BuildersKt__Builders_commonKt.launch $ default（Builders.common.kt：49）在kotlinx.coroutines.BuildersKt.launch $ default（未知来源）在kotlinx.coroutines.flow.FlowKt__CollectKt.launchIn（Collect.kt：49）在kotlinx.coroutines.flow.FlowKt.launchIn（未知来源）在app.topcafes.feed.viewmodel.FeedViewModel.bindIntents（FeedViewModel.kt：42）在app.topcafes.FeedTest $ topCafesPoc $ 1.invokeSuspend（FeedTest.kt：53）在app.topcafes.FeedTest $ topCafesPoc $ 1.invoke（FeedTest.kt）在kotlinx.coroutines.test.TestBuildersKt $ runBlockingTest $ deferred $ 1.invokeSuspend（TestBuilders.kt：50）在kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith（ContinuationImpl.kt：33）在kotlinx.coroutines.DispatchedTask.run（DispatchedTask.kt：56）在kotlinx.coroutines.test.TestCoroutineDispatcher.dispatch（TestCoroutineDispatcher.kt：50）在kotlinx.coroutines.DispatchedContinuationKt.resumeCancellableWith（DispatchedContinuation.kt：288）在kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable（Cancellable.kt：26）在kotlinx.coroutines.CoroutineStart.invoke（CoroutineStart.kt：109）在kotlinx.coroutines.AbstractCoroutine.start（AbstractCoroutine.kt：158）在kotlinx.coroutines.BuildersKt__Builders_commonKt.async（Builders.common.kt：91）在kotlinx.coroutines.BuildersKt.async（未知来源）在kotlinx.coroutines.BuildersKt__Builders_commonKt.async $ default（Builders.common.kt：84）在kotlinx.coroutines.BuildersKt.async $ default（未知来源）在kotlinx.coroutines.test.TestBuildersKt.runBlockingTest（TestBuilders.kt：49）在kotlinx.coroutines.test.TestBuildersKt.runBlockingTest（TestBuilders.kt：80）在app.topcafes.FeedTest.topCafesPoc（FeedTest.kt：47）在sun.reflect.NativeMethodAccessorImpl.invoke0（本机方法）处在sun.reflect.NativeMethodAccessorImpl.invoke（NativeMethodAccessorImpl.java:62）在sun.reflect.DelegatingMethodAccessorImpl.invoke（DelegatingMethodAccessorImpl.java:43）在java.lang.reflect.Method.invoke（Method.java:498）在org.junit.runners.model.FrameworkMethod $ 1.runReflectiveCall（FrameworkMethod.java:50）在org.junit.internal.runners.model.ReflectiveCallable.run（ReflectiveCallable.java:12）在org.junit.runners.model.FrameworkMethod.invokeExplosively（FrameworkMethod.java:47）在org.junit.internal.runners.statements.InvokeMethod.evaluate（InvokeMethod.java:17）在org.junit.runners.ParentRunner.runLeaf（ParentRunner.java:325）在org.junit.runners.BlockJUnit4ClassRunner.runChild（BlockJUnit4ClassRunner.java:78）在org.junit.runners.BlockJUnit4ClassRunner.runChild（BlockJUnit4ClassRunner.java:57）在org.junit.runners.ParentRunner $ 3.run（ParentRunner.java:290）在org.junit.runners.ParentRunner上$ 1.schedule（ParentRunner.java:71）在org.junit.runners.ParentRunner.runChildren（ParentRunner.java:288）在org.junit.runners.ParentRunner.access $ 000（ParentRunner.java:58）在org.junit.runners.ParentRunner上$ 2.evaluate（ParentRunner.java:268）在org.junit.runners.ParentRunner.run（ParentRunner.java:363）在org.junit.runner.JUnitCore.run（JUnitCore.java:137）在com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs（JUnit4IdeaTestRunner.java:68）在com.intellij.rt.junit.IdeaTestRunner $ Repeater.startRunnerWithArgs（IdeaTestRunner.java:33）在com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart（JUnitStarter.java:230）在com.intellij.rt.junit.JUnitStarter.main（JUnitStarter.java:58）由以下原因引起：java.lang.RuntimeException：android.os.Looper中的方法getMainLooper没有被模拟。有关详情，请参见http://g.co/androidstudio/not-mocked。在android.os.Looper.getMainLooper（Looper.java）在kotlinx.coroutines.android.AndroidDispatcherFactory.createDispatcher（HandlerDispatcher.kt：55）在kotlinx.coroutines.android.AndroidDispatcherFactory.createDispatcher（HandlerDispatcher.kt：52）在kotlinx.coroutines.internal.MainDispatchersKt.tryCreateDispatcher（MainDispatchers.kt：57）在kotlinx.coroutines.test.internal.TestMainDispatcher.getDelegate（MainTestDispatcher.kt：19）在kotlinx.coroutines.test.internal.TestMainDispatcher.getImmediate（MainTestDispatcher.kt：32）在androidx.lifecycle.ViewModelKt.getViewModelScope（ViewModel.kt：42）在app.topcafes.feed.viewmodel.FeedViewModel.bindIntents（FeedViewModel.kt：38） ...还有39个

Answer 1

在创建ViewModel时注入并确定CoroutineScope

在生产中，因为使用了ViewModel的coroutineScopeProvider，所以使用空viewModelScope创建了ViewModel。为了进行测试，将TestCoroutineScope作为ViewModel参数传递。

SomeUtils.kt

/**
 * Configure CoroutineScope injection for production and testing.
 *
 * @receiver ViewModel provides viewModelScope for production
 * @param coroutineScope null for production, injects TestCoroutineScope for unit tests
 * @return CoroutineScope to launch coroutines on
 */
fun ViewModel.getViewModelScope(coroutineScope: CoroutineScope?) =
    if (coroutineScope == null) this.viewModelScope
    else coroutineScope

SomeViewModel.kt

class FeedViewModel(
    private val coroutineScopeProvider: CoroutineScope? = null,
    private val repository: FeedRepository
) : ViewModel() {

    private val coroutineScope = getViewModelScope(coroutineScopeProvider)

    fun getSomeData() {
        repository.getSomeDataRequest().onEach {
            // Some code here.            
        }.launchIn(coroutineScope)
    }

}

SomeTest.kt

@ExperimentalCoroutinesApi
class FeedTest : BeforeAllCallback, AfterAllCallback {

    private val testDispatcher = TestCoroutineDispatcher()
    private val testScope = TestCoroutineScope(testDispatcher)
    private val repository = mockkClass(FeedRepository::class)
    private var loadNetworkIntent = MutableStateFlow<LoadNetworkIntent?>(null)

    override fun beforeAll(context: ExtensionContext?) {
        // Set Coroutine Dispatcher.
        Dispatchers.setMain(testDispatcher)
    }

    override fun afterAll(context: ExtensionContext?) {
        Dispatchers.resetMain()
        // Reset Coroutine Dispatcher and Scope.
        testDispatcher.cleanupTestCoroutines()
        testScope.cleanupTestCoroutines()
    }

    @Test
    fun topCafesPoc() = testDispatcher.runBlockingTest {
        ...
        val viewModel = FeedViewModel(testScope, repository)
        viewmodel.getSomeData()
        ...
    }
}

如何使用Kotlin协程为Android单元测试注入viewModelScope？

问题

预期

已观察

实施

完整错误日志

1 个答案:

在创建ViewModel时注入并确定CoroutineScope