如何使用 Kotlin 协程为 Android 单元测试注入 viewModelScope？
How to inject viewModelScope for Android unit test with Kotlin coroutines?
问题
使用 Kotlin 协程为 Android 单元测试注入 viewModelScope 的最佳策略是什么？
当 CoroutineScope 被注入到 ViewModel 进行单元测试时，CoroutineDispatcher 是否也应该被注入并使用 flowOn 定义，即使在生产代码中不需要它？
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 returns Dispathers.Main 上的数据，两者都是默认设置。
预期
运行 对保存在 Kotlin Flow 值中的 Android 的 ViewModel 视图状态值进行单元测试。
观察到
Module with the Main dispatcher had failed to initialize. For tests Dispatchers.setMain from kotlinx-coroutines-test module can be used
第一次出现硬编码 CoroutineScope 时，单元测试失败。 viewModelScope 用于启动的协程将维护 ViewModel 的生命周期。但是，viewModelScope 是从 ViewModel 内部创建的，与可以在 ViewModel 外部定义并作为参数传入的 CoroutineDispatcher 相比，这使得注入更加复杂。
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。
完整的错误日志
Exception in thread "main @coroutine#1" java.lang.IllegalStateException: Module with the Main dispatcher had failed to initialize. For tests Dispatchers.setMain from kotlinx-coroutines-test module can be used
at kotlinx.coroutines.internal.MissingMainCoroutineDispatcher.missing(MainDispatchers.kt:113)
at kotlinx.coroutines.internal.MissingMainCoroutineDispatcher.isDispatchNeeded(MainDispatchers.kt:91)
at kotlinx.coroutines.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:285)
at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:26)
at kotlinx.coroutines.CoroutineStart.invoke(CoroutineStart.kt:109)
at kotlinx.coroutines.AbstractCoroutine.start(AbstractCoroutine.kt:158)
at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch(Builders.common.kt:56)
at kotlinx.coroutines.BuildersKt.launch(Unknown Source)
at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch$default(Builders.common.kt:49)
at kotlinx.coroutines.BuildersKt.launch$default(Unknown Source)
at kotlinx.coroutines.flow.FlowKt__CollectKt.launchIn(Collect.kt:49)
at kotlinx.coroutines.flow.FlowKt.launchIn(Unknown Source)
at app.topcafes.feed.viewmodel.FeedViewModel.bindIntents(FeedViewModel.kt:38)
at app.topcafes.FeedTest$topCafesPoc.invokeSuspend(FeedTest.kt:53)
at app.topcafes.FeedTest$topCafesPoc.invoke(FeedTest.kt)
at kotlinx.coroutines.test.TestBuildersKt$runBlockingTest$deferred.invokeSuspend(TestBuilders.kt:50)
at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:56)
at kotlinx.coroutines.test.TestCoroutineDispatcher.dispatch(TestCoroutineDispatcher.kt:50)
at kotlinx.coroutines.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:288)
at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:26)
at kotlinx.coroutines.CoroutineStart.invoke(CoroutineStart.kt:109)
at kotlinx.coroutines.AbstractCoroutine.start(AbstractCoroutine.kt:158)
at kotlinx.coroutines.BuildersKt__Builders_commonKt.async(Builders.common.kt:91)
at kotlinx.coroutines.BuildersKt.async(Unknown Source)
at kotlinx.coroutines.BuildersKt__Builders_commonKt.async$default(Builders.common.kt:84)
at kotlinx.coroutines.BuildersKt.async$default(Unknown Source)
at kotlinx.coroutines.test.TestBuildersKt.runBlockingTest(TestBuilders.kt:49)
at kotlinx.coroutines.test.TestBuildersKt.runBlockingTest(TestBuilders.kt:80)
at app.topcafes.FeedTest.topCafesPoc(FeedTest.kt:47)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access[=22=]0(ParentRunner.java:58)
at org.junit.runners.ParentRunner.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)
Caused by: java.lang.RuntimeException: Method getMainLooper in android.os.Looper not mocked. See http://g.co/androidstudio/not-mocked for details.
at android.os.Looper.getMainLooper(Looper.java)
at kotlinx.coroutines.android.AndroidDispatcherFactory.createDispatcher(HandlerDispatcher.kt:55)
at kotlinx.coroutines.android.AndroidDispatcherFactory.createDispatcher(HandlerDispatcher.kt:52)
at kotlinx.coroutines.internal.MainDispatchersKt.tryCreateDispatcher(MainDispatchers.kt:57)
at kotlinx.coroutines.test.internal.TestMainDispatcher.getDelegate(MainTestDispatcher.kt:19)
at kotlinx.coroutines.test.internal.TestMainDispatcher.getImmediate(MainTestDispatcher.kt:32)
at androidx.lifecycle.ViewModelKt.getViewModelScope(ViewModel.kt:42)
... 40 more
Exception in thread "main @coroutine#1" java.lang.IllegalStateException: Module with the Main dispatcher had failed to initialize. For tests Dispatchers.setMain from kotlinx-coroutines-test module can be used
at kotlinx.coroutines.internal.MissingMainCoroutineDispatcher.missing(MainDispatchers.kt:113)
at kotlinx.coroutines.internal.MissingMainCoroutineDispatcher.isDispatchNeeded(MainDispatchers.kt:91)
at kotlinx.coroutines.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:285)
at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:26)
at kotlinx.coroutines.CoroutineStart.invoke(CoroutineStart.kt:109)
at kotlinx.coroutines.AbstractCoroutine.start(AbstractCoroutine.kt:158)
at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch(Builders.common.kt:56)
at kotlinx.coroutines.BuildersKt.launch(Unknown Source)
at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch$default(Builders.common.kt:49)
at kotlinx.coroutines.BuildersKt.launch$default(Unknown Source)
at kotlinx.coroutines.flow.FlowKt__CollectKt.launchIn(Collect.kt:49)
at kotlinx.coroutines.flow.FlowKt.launchIn(Unknown Source)
at app.topcafes.feed.viewmodel.FeedViewModel.bindIntents(FeedViewModel.kt:42)
at app.topcafes.FeedTest$topCafesPoc.invokeSuspend(FeedTest.kt:53)
at app.topcafes.FeedTest$topCafesPoc.invoke(FeedTest.kt)
at kotlinx.coroutines.test.TestBuildersKt$runBlockingTest$deferred.invokeSuspend(TestBuilders.kt:50)
at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:56)
at kotlinx.coroutines.test.TestCoroutineDispatcher.dispatch(TestCoroutineDispatcher.kt:50)
at kotlinx.coroutines.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:288)
at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:26)
at kotlinx.coroutines.CoroutineStart.invoke(CoroutineStart.kt:109)
at kotlinx.coroutines.AbstractCoroutine.start(AbstractCoroutine.kt:158)
at kotlinx.coroutines.BuildersKt__Builders_commonKt.async(Builders.common.kt:91)
at kotlinx.coroutines.BuildersKt.async(Unknown Source)
at kotlinx.coroutines.BuildersKt__Builders_commonKt.async$default(Builders.common.kt:84)
at kotlinx.coroutines.BuildersKt.async$default(Unknown Source)
at kotlinx.coroutines.test.TestBuildersKt.runBlockingTest(TestBuilders.kt:49)
at kotlinx.coroutines.test.TestBuildersKt.runBlockingTest(TestBuilders.kt:80)
at app.topcafes.FeedTest.topCafesPoc(FeedTest.kt:47)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access[=22=]0(ParentRunner.java:58)
at org.junit.runners.ParentRunner.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)
Caused by: java.lang.RuntimeException: Method getMainLooper in android.os.Looper not mocked. See http://g.co/androidstudio/not-mocked for details.
at android.os.Looper.getMainLooper(Looper.java)
at kotlinx.coroutines.android.AndroidDispatcherFactory.createDispatcher(HandlerDispatcher.kt:55)
at kotlinx.coroutines.android.AndroidDispatcherFactory.createDispatcher(HandlerDispatcher.kt:52)
at kotlinx.coroutines.internal.MainDispatchersKt.tryCreateDispatcher(MainDispatchers.kt:57)
at kotlinx.coroutines.test.internal.TestMainDispatcher.getDelegate(MainTestDispatcher.kt:19)
at kotlinx.coroutines.test.internal.TestMainDispatcher.getImmediate(MainTestDispatcher.kt:32)
at androidx.lifecycle.ViewModelKt.getViewModelScope(ViewModel.kt:42)
at app.topcafes.feed.viewmodel.FeedViewModel.bindIntents(FeedViewModel.kt:38)
... 39 more
在 ViewModel 创建时注入并确定 CoroutineScope
在生产中，ViewModel 是使用空 coroutineScopeProvider 创建的，因为使用了 ViewModel 的 viewModelScope。为了进行测试，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()
...
}
}
问题
使用 Kotlin 协程为 Android 单元测试注入
viewModelScope的最佳策略是什么？当 CoroutineScope 被注入到 ViewModel 进行单元测试时，CoroutineDispatcher 是否也应该被注入并使用
flowOn定义，即使在生产代码中不需要它？
flowOn，因为 Retrofit 在 SomeRepository.kt 中处理 Dispatchers.IO 上的线程，并且viewModelScope returns Dispathers.Main 上的数据，两者都是默认设置。
预期
运行 对保存在 Kotlin Flow 值中的 Android 的 ViewModel 视图状态值进行单元测试。
观察到
Module with the Main dispatcher had failed to initialize. For tests Dispatchers.setMain from kotlinx-coroutines-test module can be used
第一次出现硬编码 CoroutineScope 时，单元测试失败。 viewModelScope 用于启动的协程将维护 ViewModel 的生命周期。但是，viewModelScope 是从 ViewModel 内部创建的，与可以在 ViewModel 外部定义并作为参数传入的 CoroutineDispatcher 相比，这使得注入更加复杂。
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。
完整的错误日志
Exception in thread "main @coroutine#1" java.lang.IllegalStateException: Module with the Main dispatcher had failed to initialize. For tests Dispatchers.setMain from kotlinx-coroutines-test module can be used at kotlinx.coroutines.internal.MissingMainCoroutineDispatcher.missing(MainDispatchers.kt:113) at kotlinx.coroutines.internal.MissingMainCoroutineDispatcher.isDispatchNeeded(MainDispatchers.kt:91) at kotlinx.coroutines.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:285) at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:26) at kotlinx.coroutines.CoroutineStart.invoke(CoroutineStart.kt:109) at kotlinx.coroutines.AbstractCoroutine.start(AbstractCoroutine.kt:158) at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch(Builders.common.kt:56) at kotlinx.coroutines.BuildersKt.launch(Unknown Source) at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch$default(Builders.common.kt:49) at kotlinx.coroutines.BuildersKt.launch$default(Unknown Source) at kotlinx.coroutines.flow.FlowKt__CollectKt.launchIn(Collect.kt:49) at kotlinx.coroutines.flow.FlowKt.launchIn(Unknown Source) at app.topcafes.feed.viewmodel.FeedViewModel.bindIntents(FeedViewModel.kt:38) at app.topcafes.FeedTest$topCafesPoc.invokeSuspend(FeedTest.kt:53) at app.topcafes.FeedTest$topCafesPoc.invoke(FeedTest.kt) at kotlinx.coroutines.test.TestBuildersKt$runBlockingTest$deferred.invokeSuspend(TestBuilders.kt:50) at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33) at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:56) at kotlinx.coroutines.test.TestCoroutineDispatcher.dispatch(TestCoroutineDispatcher.kt:50) at kotlinx.coroutines.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:288) at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:26) at kotlinx.coroutines.CoroutineStart.invoke(CoroutineStart.kt:109) at kotlinx.coroutines.AbstractCoroutine.start(AbstractCoroutine.kt:158) at kotlinx.coroutines.BuildersKt__Builders_commonKt.async(Builders.common.kt:91) at kotlinx.coroutines.BuildersKt.async(Unknown Source) at kotlinx.coroutines.BuildersKt__Builders_commonKt.async$default(Builders.common.kt:84) at kotlinx.coroutines.BuildersKt.async$default(Unknown Source) at kotlinx.coroutines.test.TestBuildersKt.runBlockingTest(TestBuilders.kt:49) at kotlinx.coroutines.test.TestBuildersKt.runBlockingTest(TestBuilders.kt:80) at app.topcafes.FeedTest.topCafesPoc(FeedTest.kt:47) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.junit.runners.model.FrameworkMethod.runReflectiveCall(FrameworkMethod.java:50) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57) at org.junit.runners.ParentRunner.run(ParentRunner.java:290) at org.junit.runners.ParentRunner.schedule(ParentRunner.java:71) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288) at org.junit.runners.ParentRunner.access[=22=]0(ParentRunner.java:58) at org.junit.runners.ParentRunner.evaluate(ParentRunner.java:268) at org.junit.runners.ParentRunner.run(ParentRunner.java:363) at org.junit.runner.JUnitCore.run(JUnitCore.java:137) at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68) at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33) at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230) at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58) Caused by: java.lang.RuntimeException: Method getMainLooper in android.os.Looper not mocked. See http://g.co/androidstudio/not-mocked for details. at android.os.Looper.getMainLooper(Looper.java) at kotlinx.coroutines.android.AndroidDispatcherFactory.createDispatcher(HandlerDispatcher.kt:55) at kotlinx.coroutines.android.AndroidDispatcherFactory.createDispatcher(HandlerDispatcher.kt:52) at kotlinx.coroutines.internal.MainDispatchersKt.tryCreateDispatcher(MainDispatchers.kt:57) at kotlinx.coroutines.test.internal.TestMainDispatcher.getDelegate(MainTestDispatcher.kt:19) at kotlinx.coroutines.test.internal.TestMainDispatcher.getImmediate(MainTestDispatcher.kt:32) at androidx.lifecycle.ViewModelKt.getViewModelScope(ViewModel.kt:42) ... 40 more Exception in thread "main @coroutine#1" java.lang.IllegalStateException: Module with the Main dispatcher had failed to initialize. For tests Dispatchers.setMain from kotlinx-coroutines-test module can be used at kotlinx.coroutines.internal.MissingMainCoroutineDispatcher.missing(MainDispatchers.kt:113) at kotlinx.coroutines.internal.MissingMainCoroutineDispatcher.isDispatchNeeded(MainDispatchers.kt:91) at kotlinx.coroutines.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:285) at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:26) at kotlinx.coroutines.CoroutineStart.invoke(CoroutineStart.kt:109) at kotlinx.coroutines.AbstractCoroutine.start(AbstractCoroutine.kt:158) at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch(Builders.common.kt:56) at kotlinx.coroutines.BuildersKt.launch(Unknown Source) at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch$default(Builders.common.kt:49) at kotlinx.coroutines.BuildersKt.launch$default(Unknown Source) at kotlinx.coroutines.flow.FlowKt__CollectKt.launchIn(Collect.kt:49) at kotlinx.coroutines.flow.FlowKt.launchIn(Unknown Source) at app.topcafes.feed.viewmodel.FeedViewModel.bindIntents(FeedViewModel.kt:42) at app.topcafes.FeedTest$topCafesPoc.invokeSuspend(FeedTest.kt:53) at app.topcafes.FeedTest$topCafesPoc.invoke(FeedTest.kt) at kotlinx.coroutines.test.TestBuildersKt$runBlockingTest$deferred.invokeSuspend(TestBuilders.kt:50) at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33) at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:56) at kotlinx.coroutines.test.TestCoroutineDispatcher.dispatch(TestCoroutineDispatcher.kt:50) at kotlinx.coroutines.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:288) at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:26) at kotlinx.coroutines.CoroutineStart.invoke(CoroutineStart.kt:109) at kotlinx.coroutines.AbstractCoroutine.start(AbstractCoroutine.kt:158) at kotlinx.coroutines.BuildersKt__Builders_commonKt.async(Builders.common.kt:91) at kotlinx.coroutines.BuildersKt.async(Unknown Source) at kotlinx.coroutines.BuildersKt__Builders_commonKt.async$default(Builders.common.kt:84) at kotlinx.coroutines.BuildersKt.async$default(Unknown Source) at kotlinx.coroutines.test.TestBuildersKt.runBlockingTest(TestBuilders.kt:49) at kotlinx.coroutines.test.TestBuildersKt.runBlockingTest(TestBuilders.kt:80) at app.topcafes.FeedTest.topCafesPoc(FeedTest.kt:47) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.junit.runners.model.FrameworkMethod.runReflectiveCall(FrameworkMethod.java:50) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57) at org.junit.runners.ParentRunner.run(ParentRunner.java:290) at org.junit.runners.ParentRunner.schedule(ParentRunner.java:71) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288) at org.junit.runners.ParentRunner.access[=22=]0(ParentRunner.java:58) at org.junit.runners.ParentRunner.evaluate(ParentRunner.java:268) at org.junit.runners.ParentRunner.run(ParentRunner.java:363) at org.junit.runner.JUnitCore.run(JUnitCore.java:137) at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68) at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33) at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230) at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58) Caused by: java.lang.RuntimeException: Method getMainLooper in android.os.Looper not mocked. See http://g.co/androidstudio/not-mocked for details. at android.os.Looper.getMainLooper(Looper.java) at kotlinx.coroutines.android.AndroidDispatcherFactory.createDispatcher(HandlerDispatcher.kt:55) at kotlinx.coroutines.android.AndroidDispatcherFactory.createDispatcher(HandlerDispatcher.kt:52) at kotlinx.coroutines.internal.MainDispatchersKt.tryCreateDispatcher(MainDispatchers.kt:57) at kotlinx.coroutines.test.internal.TestMainDispatcher.getDelegate(MainTestDispatcher.kt:19) at kotlinx.coroutines.test.internal.TestMainDispatcher.getImmediate(MainTestDispatcher.kt:32) at androidx.lifecycle.ViewModelKt.getViewModelScope(ViewModel.kt:42) at app.topcafes.feed.viewmodel.FeedViewModel.bindIntents(FeedViewModel.kt:38) ... 39 more
在 ViewModel 创建时注入并确定 CoroutineScope
在生产中，ViewModel 是使用空 coroutineScopeProvider 创建的，因为使用了 ViewModel 的 viewModelScope。为了进行测试，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()
...
}
}