I am in the process of getting to know RxJava. I started using it in one of my personal apps and would like to unit test the code but having some difficulties and would like some help.
The scenario is simple.
UserInfo object by making a REST callUserInfo object is not null return true else return false.For the above scenario my RxJava code looks like this
public LiveData<Boolean> doesUserExists(String userName) {
UserExistsObserver observer= new UserExistsObserver ();
getUserInfo(userName).subscribeWith(subscriber);
disposable.add(observer);
return userExists;
}
public Observable<Boolean> getUserInfo(String userName) {
return repository.getUserInfo(userName)
.flatMap(new Function<UserInfo, Observable<Boolean>>() {
@Override
public Observable<Boolean> apply(UserInfo userInfo) throws Exception {
return Observable.just(userInfo != null);
}
})
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread());
}
So I wanted to write a simple unit test to check if getUserInfo() returns correct boolean value or not. Below is my unit test.
@Test
public void getUserInfo_returns_true(){
UserInfo userInfo = new UserInfo(); //Dummy data - non null userInfo object
when(repository.getUserInfo("username")).thenReturn(Observable.just(userInfo));
TestObserver<Boolean> testObserver = new TestObserver<>();
//the flatMap operator should return true since userInfo is not null
viewModel.getUserInfo("username").subscribeWith(testObserver);
testObserver.assertValue(true);
}
And below is my log
java.lang.AssertionError: Expected: true (class: Boolean), Actual: [] (latch = 1, values = 0, errors = 0, completions = 0)
at io.reactivex.observers.BaseTestConsumer.fail(BaseTestConsumer.java:163)
at io.reactivex.observers.BaseTestConsumer.assertValue(BaseTestConsumer.java:328)
at com.ik.githubbrowser.search_user.SearchUserViewModelTest.getUserInfo_returns_true(SearchUserViewModelTest.java:51)
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$1.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.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
at org.junit.rules.TestWatcher$1.evaluate(TestWatcher.java:55)
at org.junit.rules.RunRules.evaluate(RunRules.java:20)
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$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.mockito.internal.runners.JUnit45AndHigherRunnerImpl.run(JUnit45AndHigherRunnerImpl.java:37)
at org.mockito.runners.MockitoJUnitRunner.run(MockitoJUnitRunner.java:62)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:117)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:42)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:262)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:84)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
java.lang.NullPointerException
at io.reactivex.android.schedulers.HandlerScheduler$HandlerWorker.schedule(HandlerScheduler.java:70)
at io.reactivex.Scheduler$Worker.schedule(Scheduler.java:272)
at io.reactivex.internal.operators.observable.ObservableObserveOn$ObserveOnObserver.schedule(ObservableObserveOn.java:161)
at io.reactivex.internal.operators.observable.ObservableObserveOn$ObserveOnObserver.onNext(ObservableObserveOn.java:119)
at io.reactivex.internal.operators.observable.ObservableSubscribeOn$SubscribeOnObserver.onNext(ObservableSubscribeOn.java:58)
at io.reactivex.internal.operators.observable.ObservableScalarXMap$ScalarDisposable.run(ObservableScalarXMap.java:248)
at io.reactivex.internal.operators.observable.ObservableScalarXMap$ScalarXMapObservable.subscribeActual(ObservableScalarXMap.java:164)
at io.reactivex.Observable.subscribe(Observable.java:10903)
at io.reactivex.internal.operators.observable.ObservableSubscribeOn$SubscribeTask.run(ObservableSubscribeOn.java:96)
at io.reactivex.Scheduler$DisposeTask.run(Scheduler.java:452)
at io.reactivex.internal.schedulers.ScheduledRunnable.run(ScheduledRunnable.java:61)
at io.reactivex.internal.schedulers.ScheduledRunnable.call(ScheduledRunnable.java:52)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Exception in thread "RxCachedThreadScheduler-1" java.lang.NullPointerException
at io.reactivex.android.schedulers.HandlerScheduler$HandlerWorker.schedule(HandlerScheduler.java:70)
at io.reactivex.Scheduler$Worker.schedule(Scheduler.java:272)
at io.reactivex.internal.operators.observable.ObservableObserveOn$ObserveOnObserver.schedule(ObservableObserveOn.java:161)
at io.reactivex.internal.operators.observable.ObservableObserveOn$ObserveOnObserver.onNext(ObservableObserveOn.java:119)
at io.reactivex.internal.operators.observable.ObservableSubscribeOn$SubscribeOnObserver.onNext(ObservableSubscribeOn.java:58)
at io.reactivex.internal.operators.observable.ObservableScalarXMap$ScalarDisposable.run(ObservableScalarXMap.java:248)
at io.reactivex.internal.operators.observable.ObservableScalarXMap$ScalarXMapObservable.subscribeActual(ObservableScalarXMap.java:164)
at io.reactivex.Observable.subscribe(Observable.java:10903)
at io.reactivex.internal.operators.observable.ObservableSubscribeOn$SubscribeTask.run(ObservableSubscribeOn.java:96)
at io.reactivex.Scheduler$DisposeTask.run(Scheduler.java:452)
at io.reactivex.internal.schedulers.ScheduledRunnable.run(ScheduledRunnable.java:61)
at io.reactivex.internal.schedulers.ScheduledRunnable.call(ScheduledRunnable.java:52)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Process finished with exit code -1
Your method has to go through 2 different threads to produce a result (due to the subscribeOn and observeOn calls). This means the observer needs time to actually produce a result. Use TestObserver.awaitTerminalEvent() before checking assertValue to ensure the observable actually produced a value.
Alternatively you should use different schedulers when testing code, since the Android scheduler might require additional code to function properly in a testing environment.