how to pass test viewmodel with coroutines unit test correctly with mockito

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Yodgorbek Komilov

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Jun 27, 2021, 5:50:50 AM6/27/21

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I have implemented unit testing with mockito but when I run the project I am getting following exception

Exception in thread "main @coroutine#2" java.lang.NullPointerException at com.example.giphyandroidapp.viewmodel.GiphyTaskViewModel$getGifsFromText$1.invokeSuspend(GiphyTaskViewModel.kt:26) at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33) at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:106) at kotlinx.coroutines.test.TestCoroutineDispatcher.dispatch(TestCoroutineDispatcher.kt:50) at kotlinx.coroutines.test.internal.TestMainDispatcher.dispatch(MainTestDispatcher.kt:35) at kotlinx.coroutines.internal.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:305) at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:30) at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable$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)

below my ViewModelTest

import androidx.arch.core.executor.testing.InstantTaskExecutorRule import androidx.lifecycle.Observer import com.example.giphyandroidapp.model.gifsresponse.DataItem import com.example.giphyandroidapp.model.gifsresponse.GiphyResponse import com.example.giphyandroidapp.repository.GiphyTaskRepository import com.example.giphyandroidapp.utils.Constants import com.nhaarman.mockitokotlin2.eq import com.nhaarman.mockitokotlin2.mock import com.nhaarman.mockitokotlin2.verify import kotlinx.coroutines.ExperimentalCoroutinesApi import kotlinx.coroutines.runBlocking import kotlinx.coroutines.test.runBlockingTest import org.junit.Before import org.junit.Rule import org.junit.Test import org.junit.jupiter.api.extension.RegisterExtension import org.junit.rules.TestRule import org.junit.runner.RunWith import org.mockito.Mock import org.mockito.Mockito.`when` import org.mockito.junit.MockitoJUnitRunner import retrofit2.Response import kotlin.test.assertNotNull import com.example.giphyandroidapp.utils.Result @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 { giphyTaskViewModel?.getGifsFromText(Constants.Api_Key,"text", Constants.Limit) giphyTaskRepository.getGifsFromText(Constants.Api_Key,"text", Constants.Limit) giphyTaskViewModel?.giphyresponse?.observeForever(apiUsersObserver) assertNotNull(giphyTaskViewModel?.giphyresponse?.value) } } }

below my ViewModel class

@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> }