Exception in thread "main @coroutine#2" java.lang.NullPointerException in ViewModelTest?

Question

I have wrote unit testing in ViewModel with coroutines with mockito. class but I am getting following exception

 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)

below my ViewModel class where I have implemented viewmodel logic

 @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()))

            }

        }
    }

}

below Repository class

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

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

below interface class

interface GiphyTaskApiService {

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

below my ViewModel test class

 @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)




        }
    }



}

What I have tried

1.[I have tried following link][1]

I have rewrite Viewmodel logic but I am getting following exception xception in thread "main @coroutine#2" java.lang.NullPointerException at com.example.giphyandroidapp.viewmodel.GiphyTaskViewModel$getGifsFromText$1.invokeSuspend(GiphyTaskViewModel.kt:26) at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33) at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:106) at kotlinx.coroutines.test.TestCoroutineDispatcher.dispatch(TestCoroutineDispatcher.kt:50) at kotlinx.coroutines.test.internal.TestMainDispatcher.dispatch(MainTestDispatcher.kt:35) at kotlinx.coroutines.internal.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:305) at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:30) at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable$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:24) at com.example.giphyandroidapp.viewmodel.GiphyTaskViewModelTest$onCreation_fetchUserApiCalled_dataSavedToLiveData$1.invokeSuspend(GiphyTaskViewModelTest.kt:82) at com.example.giphyandroidapp.viewmodel.GiphyTaskViewModelTest$onCreation_fetchUserApiCalled_dataSavedToLiveData$1.invoke(GiphyTaskViewModelTest.kt) at com.example.giphyandroidapp.viewmodel.GiphyTaskViewModelTest$onCreation_fetchUserApiCalled_dataSavedToLiveData$1.invoke(GiphyTaskViewModelTest.kt) at kotlinx.coroutines.test.TestBuildersKt$runBlockingTest$deferred$1.invokeSuspend(TestBuilders.kt:50) at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33) at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:106) at kotlinx.coroutines.test.TestCoroutineDispatcher.dispatch(TestCoroutineDispatcher.kt:50) at kotlinx.coroutines.internal.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:305) at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:30) at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable$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.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$default(TestBuilders.kt:45) at com.example.giphyandroidapp.viewmodel.GiphyTaskViewModelTest.onCreation_fetchUserApiCalled_dataSavedToLiveData(GiphyTaskViewModelTest.kt:75) 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$1.run(DefaultInternalRunner.java:99) at org.mockito.internal.runners.DefaultInternalRunner.run(DefaultInternalRunner.java:105) at org.mockito.internal.runners.StrictRunner.run(StrictRunner.java:40) at org.mockito.junit.MockitoJUnitRunner.run(MockitoJUnitRunner.java:163) at org.junit.runner.JUnitCore.run(JUnitCore.java:137) at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69) at com.intellij.rt.junit.IdeaTestRunner$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.NullPointerException 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$1.invokeSuspend(GiphyTaskViewModelTest.kt:84) at com.example.giphyandroidapp.viewmodel.GiphyTaskViewModelTest$onCreation_fetchUserApiCalled_dataSavedToLiveData$1.invoke(GiphyTaskViewModelTest.kt) at com.example.giphyandroidapp.viewmodel.GiphyTaskViewModelTest$onCreation_fetchUserApiCalled_dataSavedToLiveData$1.invoke(GiphyTaskViewModelTest.kt) at kotlinx.coroutines.test.TestBuildersKt$runBlockingTest$deferred$1.invokeSuspend(TestBuilders.kt:50) at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33) at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:106) at kotlinx.coroutines.test.TestCoroutineDispatcher.dispatch(TestCoroutineDispatcher.kt:50) at kotlinx.coroutines.internal.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:305) at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:30) at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable$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.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$default(TestBuilders.kt:45) at com.example.giphyandroidapp.viewmodel.GiphyTaskViewModelTest.onCreation_fetchUserApiCalled_dataSavedToLiveData(GiphyTaskViewModelTest.kt:75) 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$1.run(DefaultInternalRunner.java:99) at org.mockito.internal.runners.DefaultInternalRunner.run(DefaultInternalRunner.java:105) at org.mockito.internal.runners.StrictRunner.run(StrictRunner.java:40) at org.mockito.junit.MockitoJUnitRunner.run(MockitoJUnitRunner.java:163) at org.junit.runner.JUnitCore.run(JUnitCore.java:137) at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69) at com.intellij.rt.junit.IdeaTestRunner$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)

I want to know where exactly I am making mistake what I have to inorder to pass the tests successfully

Does this answer your question? [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — Jeroen Steenbeeke, Jun 24 '21 at 09:32
Doesn't change the fact that you're invoking a method on a null object, `giphyTaskRepository` if I'm not mistaken. I would guess that `MockitoJUnitRunner` isn't detecting your `lateinit` fields. I haven't used Mockito in conjunction with Kotlin before so I can't be sure — Jeroen Steenbeeke, Jun 24 '21 at 09:38
I think that not case if you checkother places I am also lateinit fields — , Jun 24 '21 at 09:43
Put a breakpoint in your `@Before` method and check the field values? Might simply be that Mockito doesn't set them until after these are run. Again, I haven't used Mockito with Kotlin before so I'm guessing at this point (hence my commenting rather than posting an answer) — Jeroen Steenbeeke, Jun 24 '21 at 09:44
I have put break point @JeroenSteenbeeke, and debug is passing there are exception occurring DispatchedContinuation[BlockingEventLoop@59221b97, Continuation at com.example.giphyandroidapp.viewmodel.GiphyTaskViewModelTest$onCreation_fetchUserApiCalled_dataSavedToLiveData$1.invokeSuspend(GiphyTaskViewModelTest.kt:62)@1c05a54d] — , Jun 24 '21 at 09:50
So `giphyTaskRepository` is not null? Then I think your method call `getGifsFromText(apikey,text,limit)` is returning null due to that being the Mockito default for mocked classes. You need to specify what the method should return (i.e. `when(giphyTaskRepository.getGifsFromText(any(), any(), any())).thenReturn(/* some value */`) — Jeroen Steenbeeke, Jun 24 '21 at 11:15
No in addition to. You use `when()` to specify how the mock should behave, and `verify()` to check if certain methods are called — Jeroen Steenbeeke, Jun 24 '21 at 11:21
I am not sure why it is failing when I have initialized allrepository and viewmodelclass — , Jun 24 '21 at 11:26
You're using mocks (through the `@Mock` annotation), these are dummy versions of your classes that return `null` on every call by default — Jeroen Steenbeeke, Jun 24 '21 at 11:27

Jeroen Steenbeeke · Answer 1 · 2021-06-27T09:29:02.227

3

What I believe is happening is that your mocked version of GiphyTaskRepository is exhibiting the default Mockito behavior of returning null for all methods that do not have explicitly specified behavior.

As such, your call giphyTaskRepository.getGifsFromText(apikey,text,limit) in GiphyTaskViewModel returns null, causing the subsequent call to let to throw a NullPointerException.

To avoid this, you need to explicitly specify what this method should return, for instance in your setUp method:

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

  giphyTaskViewModel = GiphyTaskViewModel(giphyTaskRepository)
}

However, since you are using coroutines, it gets a bit trickier. You should include the mockito-kotlin library:

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

Next, both the GiphyTaskRepository and the method getGifsFromText need to be declared open for the mocking to work.

Finally, you need to go about stubbing a bit differently:

@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 
}

I believe your test method will then succeed

edited Jun 27 '21 at 09:29

answered Jun 24 '21 at 11:28

Jeroen Steenbeeke

3,884
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but when(giphyTaskRepository.getGifsFromText(any(),any(),any())).thenReturn(response) can be used only in fun onCreation_fetchUserApiCalled_dataSavedToLiveData() – Jun 24 '21 at 11:45
Whichever you prefer. The `when` statement can be put either in the setup method or in the test method – Jeroen Steenbeeke Jun 24 '21 at 11:48
yes but I will call that method I am getting following error warning Suspend function 'getGifsFromText' should be called only from a coroutine or another suspend function – Jun 24 '21 at 12:03
I see. It appears you need to do some extra work to use mocks with coroutines: https://github.com/mockito/mockito-kotlin/pull/357 – Jeroen Steenbeeke Jun 24 '21 at 12:11
can you suggest other ways – Jun 25 '21 at 13:13
Sorry, I'm afraid I'm out of ideas. – Jeroen Steenbeeke Jun 25 '21 at 13:23
can you check my updated post I have improved my post I have tried as you told – Jun 26 '21 at 17:48
I've updated my answer to showcase how to setup a mock for a suspend function (took some research to figure out). That said, you should probably do all given/when statements _prior_ to calling GiphyTaskViewModel's constructor. – Jeroen Steenbeeke Jun 27 '21 at 09:31
thankyou for your answer but my tests are still failing – Jun 27 '21 at 14:47

Exception in thread "main @coroutine#2" java.lang.NullPointerException in ViewModelTest?

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