How to write Unit test for ViewModel that contains RxJava/RxAndroid - unit-testing

Question

I'm trying to refactor one pretty old project, so I started implementing new architecture (MVVM) with Dagger2, RxJava, RxAndroid... Now everything is connected and working fine, now the problem is, I have no idea how to write a Unit test for my ViewModel..
I want to start with Login screen first, so I created a LoginViewModel, but first let me show you what I did..
I have a DataModule that provides 2 classes, RestApiRepository and ViewModelFactory. RestApiRepository looks like this:
public class RestApiRepository {
private RestClient restClient;
public RestApiRepository(RestClient restClient) {
this.restClient = restClient;
}
public Observable<AuthResponseEntity> authenticate(String header, AuthRequestEntity requestEntity) {
return restClient.postAuthObservable(header, requestEntity);
}
}
Rest client with api call for login:
public interface RestClient {
#POST(AUTH_URL)
Observable<AuthResponseEntity> postAuthObservable(#Header("Authorization") String authKey, #Body AuthRequestEntity requestEntity);
}
Second class from DataModule is ViewModelFactory:
#Singleton
public class ViewModelFactory extends ViewModelProvider.NewInstanceFactory implements ViewModelProvider.Factory {
private RestApiRepository repository;
#Inject
public ViewModelFactory(RestApiRepository repository) {
this.repository = repository;
}
#NonNull
#Override
public <T extends ViewModel> T create(#NonNull Class<T> modelClass) {
if (modelClass.isAssignableFrom(LoginViewModel.class)) {
return (T) new LoginViewModel(repository);
}
throw new IllegalArgumentException("Unknown class name");
}
}
And finally, LoginViewModel:
public class LoginViewModel extends ViewModel {
private final CompositeDisposable disposable = new CompositeDisposable();
private final MutableLiveData<AuthResponseEntity> responseLiveData = new MutableLiveData<>();
private RestApiRepository restApiRepository;
private SchedulerProvider provider;
public LoginViewModel(RestApiRepository restApiRepository, SchedulerProvider provider) {
this.restApiRepository = restApiRepository;
this.provider = provider;
}
public MutableLiveData<AuthResponseEntity> getResponseLiveData() {
return responseLiveData;
}
#Override
protected void onCleared() {
disposable.clear();
}
public void auth(String token, AuthRequestEntity requestEntity) {
if (token != null && requestEntity != null) {
disposable.add(restApiRepository.authenticate(token, requestEntity)
.subscribeOn(provider.io())
.observeOn(provider.ui())
.subscribeWith(new DisposableObserver<AuthResponseEntity>() {
#Override
public void onNext(AuthResponseEntity authResponseEntity) {
responseLiveData.setValue(authResponseEntity);
}
#Override
public void onError(Throwable e) {
AuthResponseEntity authResponseEntity = new AuthResponseEntity();
authResponseEntity.setErrorMessage(e.getMessage());
responseLiveData.setValue(authResponseEntity);
}
#Override
public void onComplete() {
}
}
));
}
}
}
So, I'm sure everything is connected well, I can successfuly login...
For the RxAndroid test issues, I found somewhere that I have to use this Scheduler provider like this:
public class AppSchedulerProvider implements SchedulerProvider {
public AppSchedulerProvider() {
}
#Override
public Scheduler computation() {
return Schedulers.trampoline();
}
#Override
public Scheduler io() {
return Schedulers.trampoline();
}
#Override
public Scheduler ui() {
return Schedulers.trampoline();
}
}
Below is my LoginViewModelTest class, but I don't know how to handle RxJava/RxAndroid inside the tests..
#RunWith(MockitoJUnitRunner.class)
public class LoginViewModelTest {
#Mock
private RestApiRepository restApiRepository;
#Mock
private MutableLiveData<AuthResponseEntity> mutableLiveData;
private LoginViewModel loginViewModel;
#Before
public void setUp() {
MockitoAnnotations.initMocks(this);
AppSchedulerProvider schedulerProvider = new AppSchedulerProvider();
loginViewModel = Mockito.spy(new LoginViewModel(restApiRepository, schedulerProvider));
}
#Test
public void authenticate_error() {
String token = "token";
AuthRequestEntity requestEntity = Mockito.mock(AuthRequestEntity.class);
Mockito.doReturn(Observable.error(new Throwable())).when(restApiRepository).authenticate(token, requestEntity);
loginViewModel.auth(token, requestEntity);
AuthResponseEntity responseEntity = Mockito.mock(AuthResponseEntity.class);
responseEntity.setErrorMessage("Error");
Mockito.verify(mutableLiveData).setValue(responseEntity);
}
}
So, I wanted to write a test for failed case when onError is called, but when I run it, I get this error:
exclude patterns:io.reactivex.exceptions.UndeliverableException: The exception could not be delivered to the consumer because it has already canceled/disposed the flow or the exception has nowhere to go to begin with. Further reading: https://github.com/ReactiveX/RxJava/wiki/What's-different-in-2.0#error-handling | java.lang.RuntimeException: Method getMainLooper in android.os.Looper not mocked. See http://g.co/androidstudio/not-mocked for details.

Answer 1

You can mock the behaviour of restApiRepository:
Mockito.when(restApiRepository.authenticate(token, requestEntity)).thenReturn(Observable.error(error));
and verify that responseLiveData.setValue is being called with the appropriate parameters