CODEWITHSUNDEEP
androidunit-testingkotlinjunit5
Sergio
Sergio

Reputation: 788

ViewModel UI testing with JUnit 5

I am trying to add some unit tests to my app and I am finding some problems adding tests to my ViewModel's classes.

I have created a standard ViewModel class using the androidx. lifecycle library.

Inside these ViewModel classes, I launch a Coroutine to make an API call and retrieve some data.

For this, I have created a ViewModel extension function just to call a Use Case to finally make the API call.

fun ViewModel.execute(useCase: suspend () -> Unit) {
viewModelScope.launch { useCase() }
}

As you can see, I am using viewModelScope to avoid some boilerplate code, and it is working so fine.

Also, I configured the project to use JUnit5 and Mockito. Everything goes fine until I tried to create some tests for the ViewModel class.

As I am using LiveData, I have created an Extension, to be able to catch the value of the LiveData objects. Like this:

import android.annotation.SuppressLint
import androidx.arch.core.executor.ArchTaskExecutor
import androidx.arch.core.executor.TaskExecutor
import org.junit.jupiter.api.extension.AfterEachCallback
import org.junit.jupiter.api.extension.BeforeEachCallback
import org.junit.jupiter.api.extension.ExtensionContext

/**
 * JUnit5 extension to be able to test LiveData objects
 */
class InstantExecutorExtension : BeforeEachCallback, AfterEachCallback {

    /**
     * sets a delegate before each test that updates LiveData immediately on the calling thread
     */
    @SuppressLint("RestrictedApi")
    override fun beforeEach(context: ExtensionContext?) {
        ArchTaskExecutor.getInstance()
            .setDelegate(object : TaskExecutor() {
                override fun executeOnDiskIO(runnable: Runnable) = runnable.run()

                override fun postToMainThread(runnable: Runnable) = runnable.run()

                override fun isMainThread(): Boolean = true
            })
    }

    /**
     * Remove delegate after each test, to avoid influencing other tests
     */
    @SuppressLint("RestrictedApi")
    override fun afterEach(context: ExtensionContext?) {
        ArchTaskExecutor.getInstance().setDelegate(null)
    }

}

Okay, so having this, I have read some posts about how to set up tests to be able to test ViewModel classes that use Coroutines. A lot of them explain to create a Rule, to add a TestCoroutine, to be able to launch coroutines.

import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.ExperimentalCoroutinesApi
import kotlinx.coroutines.test.TestCoroutineDispatcher
import kotlinx.coroutines.test.resetMain
import kotlinx.coroutines.test.setMain
import org.junit.rules.TestWatcher
import org.junit.runner.Description

@ExperimentalCoroutinesApi
class CoroutineTestRule(private val dispatcher: TestCoroutineDispatcher = TestCoroutineDispatcher()) :
    TestWatcher() {

    override fun starting(description: Description?) {
        super.starting(description)
        Dispatchers.setMain(dispatcher)
    }

    override fun finished(description: Description?) {
        super.finished(description)
        Dispatchers.resetMain()
    }

}

And I just need to add the rule to my ViewModel tests file and I am ready to test ViewModel classes that use coroutines and LiveData, but, when I launch my tests. I am retrieving an exception that says the following:

Exception in thread "Test worker @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:94)
    at kotlinx.coroutines.internal.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:319)
    at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:30)
    at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable$default(Cancellable.kt:25)
    at kotlinx.coroutines.CoroutineStart.invoke(CoroutineStart.kt:110)
    at kotlinx.coroutines.AbstractCoroutine.start(AbstractCoroutine.kt:126)
    at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch(Builders.common.kt:56)
    at kotlinx.coroutines.BuildersKt.launch(Unknown Source)
    at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch$default(Builders.common.kt:47)
    at kotlinx.coroutines.BuildersKt.launch$default(Unknown Source)
    at com.example.core.extensions.ViewModelExtensionKt.execute(ViewModelExtension.kt:8)
    at com.example.baseapplication.presentation.main.firstView.FirstViewModel.getSampleData(FirstViewModel.kt:21)
    at com.example.baseapplication.presentation.main.firstView.FirstViewModel.initialize(FirstViewModel.kt:17)
    at com.example.baseapplication.presentation.FirstViewModelTest$getSampleData should return sample data $1$1$1.invokeSuspend(FirstViewModelTest.kt:42)
    at com.example.baseapplication.presentation.FirstViewModelTest$getSampleData should return sample data $1$1$1.invoke(FirstViewModelTest.kt)
    at com.example.baseapplication.presentation.FirstViewModelTest$getSampleData should return sample data $1$1$1.invoke(FirstViewModelTest.kt)
    at kotlinx.coroutines.test.TestBuildersKt$runBlockingTest$deferred$1.invokeSuspend(TestBuilders.kt:50)
    at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
    at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:106)
    at kotlinx.coroutines.test.TestCoroutineDispatcher.dispatch(TestCoroutineDispatcher.kt:50)
    at kotlinx.coroutines.internal.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:322)
    at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:30)
    at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable$default(Cancellable.kt:25)
    at kotlinx.coroutines.CoroutineStart.invoke(CoroutineStart.kt:110)
    at kotlinx.coroutines.AbstractCoroutine.start(AbstractCoroutine.kt:126)
    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$default(Builders.common.kt:82)
    at kotlinx.coroutines.BuildersKt.async$default(Unknown Source)
    at kotlinx.coroutines.test.TestBuildersKt.runBlockingTest(TestBuilders.kt:49)
    at kotlinx.coroutines.test.TestBuildersKt.runBlockingTest(TestBuilders.kt:80)
    at com.example.baseapplication.presentation.FirstViewModelTest.getSampleData_should_return_sample_data_$lambda-1$lambda-0(FirstViewModelTest.kt:39)
    at org.junit.jupiter.engine.descriptor.DynamicTestTestDescriptor.lambda$execute$0(DynamicTestTestDescriptor.java:52)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131)
    at org.junit.jupiter.api.extension.InvocationInterceptor.interceptDynamicTest(InvocationInterceptor.java:161)
    at org.junit.jupiter.engine.descriptor.DynamicTestTestDescriptor.lambda$execute$1(DynamicTestTestDescriptor.java:58)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptorCall.lambda$ofVoid$0(InvocationInterceptorChain.java:78)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:106)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:64)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:45)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:37)
    at org.junit.jupiter.engine.descriptor.DynamicTestTestDescriptor.execute(DynamicTestTestDescriptor.java:57)
    at org.junit.jupiter.engine.descriptor.DynamicTestTestDescriptor.execute(DynamicTestTestDescriptor.java:31)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask$DefaultDynamicTestExecutor.execute(NodeTestTask.java:212)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask$DefaultDynamicTestExecutor.execute(NodeTestTask.java:192)
    at java.base/java.util.Optional.ifPresent(Optional.java:183)
    at org.junit.jupiter.engine.descriptor.TestFactoryTestDescriptor.lambda$invokeTestMethod$1(TestFactoryTestDescriptor.java:106)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.jupiter.engine.descriptor.TestFactoryTestDescriptor.invokeTestMethod(TestFactoryTestDescriptor.java:93)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:131)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:65)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:108)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:96)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:75)
    at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor$CollectAllTestClassesExecutor.processAllTestClasses(JUnitPlatformTestClassProcessor.java:99)
    at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor$CollectAllTestClassesExecutor.access$000(JUnitPlatformTestClassProcessor.java:79)
    at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor.stop(JUnitPlatformTestClassProcessor.java:75)
    at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.stop(SuiteTestClassProcessor.java:61)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:36)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
    at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:33)
    at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:94)
    at com.sun.proxy.$Proxy2.stop(Unknown Source)
    at org.gradle.api.internal.tasks.testing.worker.TestWorker.stop(TestWorker.java:135)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:36)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
    at org.gradle.internal.remote.internal.hub.MessageHubBackedObjectConnection$DispatchWrapper.dispatch(MessageHubBackedObjectConnection.java:182)
    at org.gradle.internal.remote.internal.hub.MessageHubBackedObjectConnection$DispatchWrapper.dispatch(MessageHubBackedObjectConnection.java:164)
    at org.gradle.internal.remote.internal.hub.MessageHub$Handler.run(MessageHub.java:414)
    at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:64)
    at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:48)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:56)
    at java.base/java.lang.Thread.run(Thread.java:834)
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)
    ... 117 more

I don't know if I am missing something or what, but I wasn't able to run the ViewModel tests and run them successfully.

I just was able to run tests successfully but it was setting the Dispatcher as Unconfined, but this is not what I want to do and also is not a recommended way.

Upvotes: 6

Views: 4440

Answers (1)

Sergio
Sergio

Reputation: 788

Okay, so I find out the problem. I was using a solution for JUnit 4, not for the JUnit 5 library.

  1. The extension I have created was right, whenever we use LiveData objects, we should update LiveData objects immediately.
  2. How I was setting up the Coroutine scope for test cases, it was wrong. I was using a solution for JUnit 4 but I should modify the code to make the same but for JUnit5.
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.ExperimentalCoroutinesApi
import kotlinx.coroutines.test.TestCoroutineDispatcher
import kotlinx.coroutines.test.TestCoroutineScope
import kotlinx.coroutines.test.resetMain
import kotlinx.coroutines.test.setMain
import org.junit.jupiter.api.extension.AfterEachCallback
import org.junit.jupiter.api.extension.BeforeEachCallback
import org.junit.jupiter.api.extension.ExtensionContext

@ExperimentalCoroutinesApi
class CoroutinesTestExtension(
   private val dispatcher: TestCoroutineDispatcher = TestCoroutineDispatcher()
) : BeforeEachCallback, AfterEachCallback, TestCoroutineScope by TestCoroutineScope(dispatcher) {

   /**
    * Set TestCoroutine dispatcher as main 
    */
   override fun beforeEach(context: ExtensionContext?) {
       Dispatchers.setMain(dispatcher)
   }

   override fun afterEach(context: ExtensionContext?) {
       Dispatchers.resetMain()
   }
}

JUnit 5 beforeEach(ExtensionContext) and afterEach(ExtensionContext) are equivalent to JUnit 4 starting(Description) and finished(Description). they are called before and after each test method annotated with @Test . The extension above will mock Dispatchers.Main before each test and reset the mock afterward.

After that, I just need to add my extensions to my test file like the following:

@ExtendWith(InstantExecutorExtension::class, CoroutinesTestExtension::class)

Upvotes: 7

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