如何为包含 RxJava/RxAndroid 的 ViewModel 编写单元测试

Question

我正在尝试重构一个相当老的项目，所以我开始使用 Dagger2、RxJava、RxAndroid 实现新架构 (MVVM)... 现在一切都已连接并且工作正常，现在问题是，我不知道如何为我的 ViewModel 编写单元测试..

我想先从登录屏幕开始，所以我创建了一个 LoginViewModel，但首先让我向您展示我所做的......

我有一个 DataModule，它提供 2 个类，RestApiRepository 和 ViewModelFactory。 RestApiRepository 看起来像这样：

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);
}
}

使用 api 调用登录的 Rest 客户端：

public interface RestClient {

@POST(AUTH_URL)
Observable<AuthResponseEntity> postAuthObservable(@Header("Authorization") String authKey, @Body AuthRequestEntity requestEntity);
}

DataModule 的第二个类是 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");
}
}

最后，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() {

                                   }
                               }
                ));
    }
}
}

所以，我确定一切都连接好了，我可以成功登录...

对于 RxAndroid 测试问题，我发现某处我必须像这样使用此调度程序提供程序：

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();
}
}

下面是我的 LoginViewModelTest 类，但我不知道如何在测试中处理 RxJava/RxAndroid..

@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);
}
}

所以，我想在调用 onError 时为失败的情况编写一个测试，但是当我运行它时，我得到了这个错误：

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

你可以模拟restApiRepository的行为：

Mockito.when(restApiRepository.authenticate(token, requestEntity)).thenReturn(Observable.error(error));

并验证 responseLiveData.setValue 是否使用适当的参数被调用