Android unit test: Mockito, Retrofit, Robolectric

Example of mocking Retrofit method call

//MODEL CLASS

interface Model{
        void init(Gson gson);
        public Single<List<ImgAlbum>> getPhotos();
    }
    
 /**
 * @author Hilfritz Camallere on 6/11/18
 */
@RunWith(RobolectricTestRunner.class)
@Config(manifest= Config.NONE)
public class MainPresenterUnitTest {
    //NEED THIS TO MAKE SURE THE TEST IS DONE IN ONE SAME THREAD
    ThreadHandler threadHandler = new ThreadHandler() {
        @Override
        public Scheduler iOThread() {
            return Schedulers.trampoline();
        }
        @Override
        public Scheduler mainThread() {
            return Schedulers.trampoline();
        }
    };
    //USEFUL IF YOU HAVE DELAYS() IN SOME OBSERVABLES
    TestScheduler testScheduler = new TestScheduler();
    MainPresenter mainPresenter;
    @Mock
    MainPresenter.MainView mainView;
    @Mock
    MainPresenter.Model model;
    
    @Before
    public void setup(){
        RxJavaPlugins.reset();
        mainPresenter = new MainPresenterImpl();
        model = Mockito.mock(MainPresenter.Model.class);
        mainView = Mockito.mock(MainPresenter.MainView.class);
        LIST.add(new ImgAlbum("title", "description", 0));
        LIST.add(new ImgAlbum("title2", "description2", 1));
        LIST.add(new ImgAlbum("title3", "description3", 2));
    }

    @After
    public void destroy(){
        RxJavaPlugins.reset();
        mainPresenter = null;
        model = null;
        mainView = null;
    }

    

    /**
    * IMPORTANT: THIS MUST BE CALLED BEFORE YOU START EXECUTING OBSERVABLES WITH DELAYS
    */
    private void setComputationSchedulerHandler() {
        RxJavaPlugins.setComputationSchedulerHandler(new Function<Scheduler, Scheduler>() {
            @Override
            public Scheduler apply(Scheduler scheduler) throws Exception {
                return testScheduler;
            }
        });
    }
    
    @Test
    public void successRefreshListEmptyTest(){
        setComputationSchedulerHandler();
        Mockito.when(model.getPhotos()).thenReturn(Single.just(EMPTY_LIST));
        mainPresenter.init(mainView, model, threadHandler);
        mainPresenter.refresh();  //NOTE:  #REFRESH() IMPLEMENTATION HAS 800MS DELAY
        testScheduler.advanceTimeBy(800, TimeUnit.MILLISECONDS);    //IMPORTANT: 800MS DELAY IN REFRESH IS REFLECTED HERE
        Mockito.verify(mainView, Mockito.times(2)).showPDialog();
        Mockito.verify(mainView, Mockito.atLeastOnce()).stopScroll();
        Mockito.verify(mainView, Mockito.never()).notifyListData();
        Mockito.verify(mainView, Mockito.times(1)).showDataNotAvailableDialog();
        Mockito.verify(mainView, Mockito.never()).showNoInternetError();
        Mockito.verify(mainView, Mockito.never()).showSomethingWentWrong();
        Mockito.verify(mainView, Mockito.atLeastOnce()).hidePDialog();
    }
    
    @Test
    public void errorLoadListNoInternetTest(){
        final IOException exception = new IOException("noInternet");
        Mockito.when(model.getPhotos()).thenReturn(Single.error(exception));  //IMPORTANT: SIMULATES THE EXCEPTION FOR NO INTERNET CONNECTION
                              //allows the subscriber's onError() method to be called
        mainPresenter.init(mainView, model, threadHandler);
        mainPresenter.run();
        Mockito.verify(mainView, Mockito.atLeastOnce()).showPDialog();
        Mockito.verify(mainView, Mockito.never()).notifyListData();
        Mockito.verify(mainView, Mockito.never()).showDataNotAvailableDialog();
        Mockito.verify(mainView, Mockito.never()).showSomethingWentWrong();
        Mockito.verify(mainView, Mockito.atLeastOnce()).hidePDialog();
        Mockito.verify(mainView, Mockito.times(1)).showNoInternetError();
    }
    
}