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问题：

线程“main@coroutine#2”java中出现异常。ViewModelTest中的lang.NullPointerException？

阎元徽
2023-03-14

我在ViewModel中编写了单元测试，并与mockito协作。类，但我得到以下异常

 Exception in thread "main @coroutine#2" java.lang.NullPointerException
    at com.example.giphyandroidapp.viewmodel.GiphyTaskViewModel$getGifsFromText$1.invokeSuspend(GiphyTaskViewModel.kt:24)
    at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
    at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:106)
    at kotlinx.coroutines.test.TestCoroutineDispatcher.dispatch(TestCoroutineDispatcher.kt:50)
    at kotlinx.coroutines.test.internal.TestMainDispatcher.dispatch(MainTestDispatcher.kt:35)
    at kotlinx.coroutines.internal.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:305)
    at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:30)
    at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable$default(Cancellable.kt:27)
    at kotlinx.coroutines.CoroutineStart.invoke(CoroutineStart.kt:110)
    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 com.example.giphyandroidapp.viewmodel.GiphyTaskViewModel.getGifsFromText(GiphyTaskViewModel.kt:22)
    at com.example.giphyandroidapp.viewmodel.GiphyTaskViewModelTest$onCreation_fetchUserApiCalled_dataSavedToLiveData$1.invokeSuspend(GiphyTaskViewModelTest.kt:61)
    at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
    at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:106)
    at kotlinx.coroutines.EventLoopImplBase.processNextEvent(EventLoop.common.kt:274)
    at kotlinx.coroutines.BlockingCoroutine.joinBlocking(Builders.kt:84)
    at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking(Builders.kt:59)
    at kotlinx.coroutines.BuildersKt.runBlocking(Unknown Source)
    at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking$default(Builders.kt:38)
    at kotlinx.coroutines.BuildersKt.runBlocking$default(Unknown Source)
    at com.example.giphyandroidapp.viewmodel.GiphyTaskViewModelTest.onCreation_fetchUserApiCalled_dataSavedToLiveData(GiphyTaskViewModelTest.kt:57)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
    at org.mockito.internal.runners.DefaultInternalRunner$1$1.evaluate(DefaultInternalRunner.java:54)
    at com.example.giphyandroidapp.viewmodel.TestCoroutineRule$apply$1.evaluate(TaskCoroutineRule.kt:22)
    at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
    at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
    at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
    at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
    at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
    at org.mockito.internal.runners.DefaultInternalRunner$1.run(DefaultInternalRunner.java:99)
    at org.mockito.internal.runners.DefaultInternalRunner.run(DefaultInternalRunner.java:105)
    at org.mockito.internal.runners.StrictRunner.run(StrictRunner.java:40)
    at org.mockito.junit.MockitoJUnitRunner.run(MockitoJUnitRunner.java:163)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:115)
    at org.junit.vintage.engine.execution.RunnerExecutor.execute(RunnerExecutor.java:42)
    at org.junit.vintage.engine.VintageTestEngine.executeAllChildren(VintageTestEngine.java:80)
    at org.junit.vintage.engine.VintageTestEngine.execute(VintageTestEngine.java:72)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:107)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:114)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:86)
    at org.junit.platform.launcher.core.DefaultLauncherSession$DelegatingLauncher.execute(DefaultLauncherSession.java:86)
    at org.junit.platform.launcher.core.SessionPerRequestLauncher.execute(SessionPerRequestLauncher.java:53)
    at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:71)
    at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
    at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:220)
    at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:53)


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 androidx.arch.core.executor.DefaultTaskExecutor.isMainThread(DefaultTaskExecutor.java:77)
    at androidx.arch.core.executor.ArchTaskExecutor.isMainThread(ArchTaskExecutor.java:116)
    at androidx.lifecycle.LiveData.assertMainThread(LiveData.java:486)
    at androidx.lifecycle.LiveData.observeForever(LiveData.java:224)
    at com.example.giphyandroidapp.viewmodel.GiphyTaskViewModelTest$onCreation_fetchUserApiCalled_dataSavedToLiveData$1.invokeSuspend(GiphyTaskViewModelTest.kt:63)
    at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
    at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:106)
    at kotlinx.coroutines.EventLoopImplBase.processNextEvent(EventLoop.common.kt:274)
    at kotlinx.coroutines.BlockingCoroutine.joinBlocking(Builders.kt:84)
    at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking(Builders.kt:59)
    at kotlinx.coroutines.BuildersKt.runBlocking(Unknown Source)
    at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking$default(Builders.kt:38)
    at kotlinx.coroutines.BuildersKt.runBlocking$default(Unknown Source)
    at com.example.giphyandroidapp.viewmodel.GiphyTaskViewModelTest.onCreation_fetchUserApiCalled_dataSavedToLiveData(GiphyTaskViewModelTest.kt:57)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
    at org.mockito.internal.runners.DefaultInternalRunner$1$1.evaluate(DefaultInternalRunner.java:54)
    at com.example.giphyandroidapp.viewmodel.TestCoroutineRule$apply$1.evaluate(TaskCoroutineRule.kt:22)
    at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
    at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
    at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
    at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
    at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
    at org.mockito.internal.runners.DefaultInternalRunner$1.run(DefaultInternalRunner.java:99)
    at org.mockito.internal.runners.DefaultInternalRunner.run(DefaultInternalRunner.java:105)
    at org.mockito.internal.runners.StrictRunner.run(StrictRunner.java:40)
    at org.mockito.junit.MockitoJUnitRunner.run(MockitoJUnitRunner.java:163)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:115)
    at org.junit.vintage.engine.execution.RunnerExecutor.execute(RunnerExecutor.java:42)
    at org.junit.vintage.engine.VintageTestEngine.executeAllChildren(VintageTestEngine.java:80)
    at org.junit.vintage.engine.VintageTestEngine.execute(VintageTestEngine.java:72)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:107)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:114)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:86)
    at org.junit.platform.launcher.core.DefaultLauncherSession$DelegatingLauncher.execute(DefaultLauncherSession.java:86)
    at org.junit.platform.launcher.core.SessionPerRequestLauncher.execute(SessionPerRequestLauncher.java:53)
    at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:71)
    at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
    at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:220)
    at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:53)

在我的ViewModel类下面，我在其中实现了视图模型逻辑

 @HiltViewModel
class GiphyTaskViewModel
@Inject
constructor(private val giphyTaskRepository: GiphyTaskRepository):ViewModel()
{
    var giphyresponse = MutableLiveData<Result<List<DataItem>?>>()



    fun getGifsFromText(apikey:String,text:String,limit:Int)= viewModelScope.launch {
        giphyTaskRepository.getGifsFromText(apikey,text,limit).let { response->
            if(response?.isSuccessful){
                var list=response.body()?.data
                giphyresponse.postValue(Success(list))
            }else{
                Error(Exception(response.message()))

            }

        }
    }

}

低于存储库类

class GiphyTaskRepository
@Inject
constructor(private val giphyTaskApiService: GiphyTaskApiService)
{

    suspend fun getGifsFromText(apikey:String,text:String,limit:Int)=
        giphyTaskApiService.getGifsFromText(apikey,text,limit)
}

接口类下面

接口GiphyTaskApiService{

    @GET("gifs/search")
    suspend fun getGifsFromText(
        @Query("api_key") api_key:String,
        @Query("q") q:String ,
        @Query("limit") limit:Int
    ):Response<GiphyResponse>
}

低于我的ViewModel测试类

 @ExperimentalCoroutinesApi
@RunWith(MockitoJUnitRunner::class)
class GiphyTaskViewModelTest {







    @Mock
    private lateinit var apiUsersObserver: Observer<Result<List<DataItem>?>>


    @RegisterExtension
    @JvmField
    @get:Rule
    val testInstantTaskExecutorRule: TestRule = InstantTaskExecutorRule()

    @get:Rule
   val testCoroutineRule = TestCoroutineRule()
    @Mock
     var giphyTaskViewModel:GiphyTaskViewModel? = null

    @Mock
     lateinit var  giphyTaskRepository:GiphyTaskRepository








    @Before
     fun setUp() {


        /* Create a mock response */;
        /* Create a mock response */;


                giphyTaskViewModel = GiphyTaskViewModel(giphyTaskRepository)
        }

    @Test
    fun onCreation_fetchUserApiCalled_dataSavedToLiveData() {
        runBlockingTest {



            val response: Response<GiphyResponse> = mock()


            giphyTaskViewModel?.getGifsFromText(Constants.Api_Key,"text", Constants.Limit)
           `when`(giphyTaskRepository.getGifsFromText(Constants.Api_Key,"text", Constants.Limit)).thenReturn(response)
            giphyTaskViewModel?.giphyresponse?.observeForever(apiUsersObserver)
            assertNotNull(giphyTaskViewModel?.giphyresponse?.value)




        }
    }



}

我试过的

1。[我尝试了以下链接][1]

onCreation_fetchUserApiCalled_dataSavedToLiveDataNullPointerException atonCreation_fetchUserApiCalled_dataSavedToLiveDataDefaultTaskEonCreation_fetchUserApiCalled_dataSavedToLiveDataMainThread（DefaultTaskEBuildersKt__Builders_commonKt）atBuildersKt__Builders_commonKtArchTaskEkotlin.coroutines.jvm.internal.MainThread（ArchTaskEmpl.resume）atmpl.kt:33LiveDkotlinx.coroutines.MainThread（LiveDask.run）atask.kt:106LiveDkotlinx.coroutines.test.Forever（LiveDispatcher.dispatch）atcom.example.giphyandroidapp.viewmodel.GihyTaskViewModelTest$1.invoke$1.invokeSuspend（GihyTaskViewModelTest.kt:84）atcom.example.giphyandroidapp.viewmodel.GihyTaskViewModelTest$est.kt$1.invoke（GihyTaskViewModelTest.kt）atcom.example.giphyandroidapp.viewmodel.GihyTaskViewModelTest$kotlinx.coroutines.test.$java.lang.（GihyTaskViewModelTandroidx.arch.core.executor.）atxecutor.isTestBuildersKt$runBlockingTest$递延$xecutor.java:77Suspend（TestBandroidx.arch.core.executor.）atxecutor.isBaseContinuationIxecutor.java:116（ContinuationIandroidx.lifecycle.）atata.assertDispatchedTata.java:486（DispatchedTandroidx.lifecycle.）atata.observeTestCoroutineData.java:224（TestCoroutineDispatcher. kt： 50）at kotlinx. coroutines。调度TestBuildersKt. runBlockingTest$default（TestBuilders. kt： 45）at com. example. giphaandroidapp. viewmodel。GihyTaskViewModelTest。onCreation_fetchUserApiCalled_dataSavedToLiveData（GihyTaskViewModelTest. kt： 75）at java. base/jdk. interal.反射。java. base/jdk. interal.反射的NativeMethod odAccessorInm.调用0（本机方法）。java. base/jdk. interal.反射的NativeMethod odAccessorInm.调用（NativeMethod odAccessorInm. java： 62）。java. base/java. lang.反射的委托方法访问Inm.调用（委托方法访问Inm. java： 43）。方法调用（方法. java： 566）at org. jite. runners. model。FrameworkMethod od1美元. runReflectiveCall（FrameworkMethod. java家长跑步者1美元.时间表（家长跑步者. java： 79）在org. jite. runners。家长跑步者. runUNICEF（家长跑步者. java： 329）在org. jite. runners。家长跑步者.访问100美元（家长跑步者. java： 66）在org. jite. runners。家长跑步者2美元.评估（家长跑步者. java： 293）在org. jite. runners。家长跑步者.评估（家长跑步者. java： 306）在org. jite. runners。家长跑步者. run（家长跑步者. java： 413）在org. mockito.内部. runners。在org. mockito.内部. runners的DefaultInternalRunner1美元. run（DefaultInternalRunner. java： 99）。在org. mockito的DefaultInternalRunner. run（DefaultInternalRunner. java： 105

我想知道我到底在哪里犯了错误，为了成功通过测试我必须做什么

共有1个答案

翟理
2023-03-14

我认为，您的模拟版本的GiphyTaskRepository显示了默认的Mockito行为，即对于所有没有明确指定行为的方法返回null。

因此，您在GihyTaskViewModel中调用gihyTaskRepository.getGifsFromText（apikey， text， limited）返回null，导致后续调用let抛出NullPointerException。

为了避免这种情况，您需要明确指定此方法应返回的内容，例如在您的设置方法中：

@Before
fun setUp() {
  val response: Response<GiphyResponse> = /* Create a mock response */;
  when(giphyTaskRepository.getGifsFromText(any(),any(),any())).thenReturn(response);

  giphyTaskViewModel = GiphyTaskViewModel(giphyTaskRepository)
}

然而，由于您使用的是协同程序，所以它变得有点棘手。您应该包括mockito kotlin库：

testImplementation "org.mockito.kotlin:mockito-kotlin:x.x.x"

接下来，需要声明GiphyTaskRepository和方法getGifsFromText以使模拟生效。

最后，您需要以不同的方式处理存根：

@Before
fun setUp() = runBlocking { // This bit is important
  val response: Response<GiphyResponse> = /* Create a mock response */;
  given(giphyTaskRepository.getGifsFromText(any(),any(),any())).willSuspendableAnswer {
                response
            }
  giphyTaskViewModel = GiphyTaskViewModel(giphyTaskRepository)

  Unit 
}

我相信你的测试方法会成功的

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