Clean Architecture - Android

 public interface TasksDataSource {

    void getTask(@NonNull String taskId, @NonNull GetTaskCallback callback);

    void saveTask(@NonNull Task task);

    void completeTask(@NonNull Task task);

    void deleteTask(@NonNull String taskId);
}

public final class Task {
    private final String mId;
    private final String mTitle;
    private final String mDescription;
    private final boolean mCompleted;
    // ... ...
}

public class CompleteTask extends UseCase<CompleteTask.RequestValues, CompleteTask.ResponseValue> {

    private final TasksRepository mTasksRepository;

    @Override
    protected void executeUseCase(final RequestValues values) {
        String completedTask = values.getCompletedTask();
        mTasksRepository.completeTask(completedTask);
        getUseCaseCallback().onSuccess(new ResponseValue());
    }
}

public class Statistics {
   private final int completedTasks;
   private final int activeTasks;
   //... ...
}

public class GetStatistics extends UseCase<GetStatistics.RequestValues, GetStatistics.ResponseValue> {

    private final TasksRepository mTasksRepository;

    @Override
    protected void executeUseCase(RequestValues requestValues) {
        mTasksRepository.getTasks(new TasksDataSource.LoadTasksCallback() {
            @Override
            public void onTasksLoaded(List<Task> tasks) {
                int activeTasks = 0;
                int completedTasks = 0;
                // We calculate number of active and completed tasks
            }
        });
    }

 public class TasksPresenter implements TasksContract.Presenter {

    private final TasksContract.View mTasksView;
    private final GetTasks mGetTasks;
    private final CompleteTask mCompleteTask;

    private void loadTasks(boolean forceUpdate, final boolean showLoadingUI) {
        

        GetTasks.RequestValues requestValue = new GetTasks.RequestValues(forceUpdate,
                mCurrentFiltering);

        mUseCaseHandler.execute(mGetTasks, requestValue,
                new UseCase.UseCaseCallback<GetTasks.ResponseValue>() {
                    @Override
                    public void onSuccess(GetTasks.ResponseValue response) {
                        // ... ...
                    }

                    @Override
                    public void onError() {
                        // The view may not be able to handle UI updates anymore
                        if (!mTasksView.isActive()) {
                            return;
                        }
                        mTasksView.showLoadingTasksError();
                    }
                });
    }

}

@RunWith(AndroidJUnit4.class)
public class TasksScreenTest {
      private void createTask(String title, String description) {
        // Click on the add task button
        onView(withId(R.id.fab_add_task)).perform(click());

        // Add task title and description
        onView(withId(R.id.add_task_title)).perform(typeText(title),
                closeSoftKeyboard()); // Type new task title
        onView(withId(R.id.add_task_description)).perform(typeText(description),
                closeSoftKeyboard()); // Type new task description and close the keyboard

        // Save the task
        onView(withId(R.id.fab_edit_task_done)).perform(click());
    }
    // ... ...
}

public class TasksPresenterTest {
       @Test
   public void completeTask_ShowsTaskMarkedComplete() {
       // Given a stubbed task
       Task task = new Task("Details Requested", "For this task");

       // When task is marked as complete
       mTasksPresenter.completeTask(task);

       // Then repository is called and task marked complete UI is shown
       verify(mTasksRepository).completeTask(eq(task.getId()));
       verify(mTasksView).showTaskMarkedComplete();
   }
   //... ...
}