Android Architecture Components - A Testable Approach to Android Development

Developing Android Apps has notoriously been a difficult task. Previously, Google refrained from giving advice as to how you should go about architecting your Android applications and it has been “left it up to the reader” to decide how. This lead to apps having a lot of bloat in their activities and being really difficult to test. This has now changed since Google I/O 2017 where the new Android Architecture components were introduced. The libraries aim to make developing and maintaining your Android apps a lot easier. In this presentation, Rebecca will present the components and dive into detail around the different types of tests you should write (and where) for your newly architected Android application.

Rebecca Franks is an Android Engineer at Over, currently building the Android version of the already popular photo editing iOS app. She is a Google Developer Expert for Android and she enjoys public speaking by frequently speaking at conferences and local meetups. Her blog has been featured multiple times on Android Weekly and she loves travelling the world.

Transcript

1. @riggaroo
   Android Architecture
   Components
   A Testable Approach to Android
   Development
   Rebecca Franks
   

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2. HELLO!
   I am Rebecca Franks
   Android Developer
   Google Developer Expert
   @riggaroo
   

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3. What are the Android Architecture Components?
   Powerful APIs that
   are testable
   "
   Improve
   app quality
   ✅
   Address common
   issues
   
   Best practice
   guidelines
   %
   

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4. @riggaroo
   Components
   - Room
   - ViewModels
   - LiveData *
   - Lifecycle *
   - Paging Library *
   - …
   

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5. Architecting an App
   

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6. bit.ly/android-arch
   bit.ly/android-arch-kotlin
   

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7. MVVM
   Model, View, ViewModel
   

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8. MVVM
   View
   ViewModel
   Model
   

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9. View
   ViewModel
   Model
   Retrofit API
   Room Database
   Web
   Service
   SQLite
   MVVM
   

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10. View
    ViewModel
    Model
    Retrofit API
    Room Database
    Web
    Service
    SQLite
    MVVM
    

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11. Room - SQLite
    Object Mapper
    

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12. Creating an Entity
    @Entity(tableName = TABLE_NAME)
    public class Event {
    @PrimaryKey(autoGenerate = true)
    private int id;
    private String name;
    private LocalDateTime date;
    public int getId() {
    return id;
    }
    public String getName() {
    return name;
    }
    public LocalDateTime getDate() {
    return date;
    }
    }
    

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13. Creating a DAO
    @Dao
    public interface EventDao {
    @Insert(onConflict = OnConflictStrategy.REPLACE)
    void addEvent(Event event);
    @Query("SELECT * FROM " + Event.TABLE_NAME + " WHERE " + Event.DATE_FIELD + " > :minDate")
    LiveData> getEvents(LocalDateTime minDate);
    }
    

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14. Creating a Database
    @Database(entities = {Event.class}, version = 1)
    public abstract class EventDatabase extends RoomDatabase {
    public abstract EventDao eventDao();
    }
    

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15. Create an instance of the DB
    @Provides
    @Singleton
    EventDatabase providesEventDatabase(CountdownApplication context) {
    return Room.databaseBuilder(context, EventDatabase.class,
    “event.db").build();
    }
    

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16. Model
    

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17. View
    ViewModel
    Model
    Retrofit API
    Room Database
    Web
    Service
    SQLite
    MVVM
    

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18. Model
    Model layer follows Repository pattern
    ie EventRepository, LoginRepository
    MVVM - Model
    

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19. Repository
    

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20. Repository
    Business Logic, Caching
    Plain object
    No Android Dependencies
    

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21. public class EventRepositoryImpl implements EventRepository {
    @Inject
    EventDao eventDao;
    public EventRepositoryImpl(EventDao eventDao) {
    this.eventDao = eventDao;
    }
    @Override
    public Completable addEvent(Event event) {
    if (event == null){
    return Completable.error(new IllegalArgumentException("Event cannot be null"));
    }
    return Completable.fromAction(() -> eventDao.addEvent(event));
    }
    }
    

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22. public class EventRepositoryImpl implements EventRepository {
    @Inject
    EventDao eventDao;
    public EventRepositoryImpl(EventDao eventDao) {
    this.eventDao = eventDao;
    }
    @Override
    public Completable addEvent(Event event) {
    if (event == null){
    return Completable.error(new IllegalArgumentException("Event cannot be null"));
    }
    return Completable.fromAction(() -> eventDao.addEvent(event));
    }
    }
    Completable is used when the Observable has to
    do some task without emitting a value.
    

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23. ViewModel
    

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24. View
    ViewModel
    Model
    Retrofit API
    Room Database
    Web
    Service
    SQLite
    MVVM
    

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25. ViewModel
    AddEventViewModel, EventListViewModel
    MVVM - ViewModel
    

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26. What is a ViewModel?
    - The VM in MVVM architecture
    - Store & manage UI-related
    data
    - Data survives config changes
    - No leaks
    

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27. public class AddEventViewModel extends ViewModel {
    @Inject
    EventRepository eventRepository;
    private String eventName;
    private String eventDescription;
    private LocalDateTime eventDateTime ;
    @Inject
    AddEventViewModel() {
    eventDateTime = LocalDateTime.now();
    }
    void addEvent() {
    Event event = new Event(0, eventName, eventDescription, eventDateTime);
    eventRepository.addEvent(event).observeOn(AndroidSchedulers.mainThread())
    .subscribeOn(Schedulers.io())
    .subscribe(new CompletableObserver() {
    @Override
    public void onSubscribe(Disposable d) {
    }
    Creating your ViewModel
    

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28. @Inject
    AddEventViewModel() {
    eventDateTime = LocalDateTime.now();
    }
    void addEvent() {
    Event event = new Event(0, eventName, eventDescription, eventDateTime);
    eventRepository.addEvent(event).observeOn(AndroidSchedulers.mainThread())
    .subscribeOn(Schedulers.io())
    .subscribe(new CompletableObserver() {
    @Override
    public void onSubscribe(Disposable d) {
    }
    @Override
    public void onComplete() {
    Log.d(TAG, ”onComplete - successfully added event");
    }
    @Override
    public void onError(Throwable e) {
    Log.d(TAG, e, "onError - add:");
    }
    });
    }
    

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29. @Inject
    AddEventViewModel() {
    eventDateTime = LocalDateTime.now();
    }
    void addEvent() {
    Event event = new Event(0, eventName, eventDescription, eventDateTime);
    eventRepository.addEvent(event).observeOn(AndroidSchedulers.mainThread())
    .subscribeOn(Schedulers.io())
    .subscribe(new CompletableObserver() {
    @Override
    public void onSubscribe(Disposable d) {
    }
    @Override
    public void onComplete() {
    Log.d(TAG, ”onComplete - successfully added event");
    }
    @Override
    public void onError(Throwable e) {
    Log.d(TAG, e, "onError - add:");
    }
    });
    }
    

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30. View
    

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31. View
    ViewModel
    Model
    Retrofit API
    Room Database
    Web
    Service
    SQLite
    MVVM
    

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32. View
    AddEventFragment, EventListFragment
    MVVM - View
    

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33. public class AddEventFragment extends Fragment {
    private Button buttonAddEvent;
    private AddEventViewModel addEventViewModel;
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle
    savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_add_event, container, false);
    //..
    setupClickListeners();
    setupViewModel();
    return view;
    }
    private void setupViewModel() {
    addEventViewModel = ViewModelProviders.of(this).get(AddEventViewModel.class);
    }
    private void setupClickListeners() {
    buttonAddEvent.setOnClickListener(v -> {
    addEventViewModel.addEvent();
    getActivity().finish();
    });
    }
    }
    

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34. public class AddEventFragment extends Fragment {
    private Button buttonAddEvent;
    private AddEventViewModel addEventViewModel;
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle
    savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_add_event, container, false);
    //..
    setupClickListeners();
    setupViewModel();
    return view;
    }
    private void setupViewModel() {
    addEventViewModel = ViewModelProviders.of(this).get(AddEventViewModel.class);
    }
    private void setupClickListeners() {
    buttonAddEvent.setOnClickListener(v -> {
    addEventViewModel.addEvent();
    getActivity().finish();
    });
    }
    }
    

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35. public class AddEventFragment extends Fragment {
    private Button buttonAddEvent;
    private AddEventViewModel addEventViewModel;
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle
    savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_add_event, container, false);
    //..
    setupClickListeners();
    setupViewModel();
    return view;
    }
    private void setupViewModel() {
    addEventViewModel = ViewModelProviders.of(this).get(AddEventViewModel.class);
    }
    private void setupClickListeners() {
    buttonAddEvent.setOnClickListener(v -> {
    addEventViewModel.addEvent();
    getActivity().finish();
    });
    }
    }
    

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36. public class AddEventFragment extends Fragment {
    private Button buttonAddEvent;
    private AddEventViewModel addEventViewModel;
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle
    savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_add_event, container, false);
    //..
    setupClickListeners();
    setupViewModel();
    return view;
    }
    private void setupViewModel() {
    addEventViewModel = ViewModelProviders.of(this).get(AddEventViewModel.class);
    }
    private void setupClickListeners() {
    buttonAddEvent.setOnClickListener(v -> {
    addEventViewModel.addEvent();
    getActivity().finish();
    });
    }
    }
    

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37. Demo
    

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39. Let’s chat about
    tests…
    

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41. View
    ViewModel
    Model
    Retrofit API
    Room Database
    Web
    Service
    SQLite
    JUnit tests
    MVVM
    

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42. View
    ViewModel
    Model
    Retrofit API
    Room Database
    Web
    Service
    SQLite
    Instrumentation Tests
    MVVM
    

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43. Abstract out Android
    Logic as much as
    possible.
    Write plenty of JUnit
    Tests, not as many UI
    Tests
    

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45. @riggaroo
    JUnit Tests
    - Run on JVM
    - No Android Dependencies
    - Use Mockito - mock out everything
    but current class under test
    

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46. @riggaroo
    Instrumentation Tests
    - Two Types:
    - Android Unit Test
    - Use Android dependencies
    - No UI
    - UI Test
    - Use Espresso
    - Physical clicks on device
    - Hardly any mocking (maybe HTTP
    responses)
    

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47. Testing Database
    Queries
    

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48. View
    ViewModel
    Model
    Retrofit API
    Room Database
    Web
    Service
    SQLite
    Testing Room
    

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49. @RunWith(AndroidJUnit4.class)
    public class EventDaoTest {
    EventDao eventDao;
    EventDatabase eventDatabase;
    @Before
    public void setup() {
    eventDatabase = Room.inMemoryDatabaseBuilder(InstrumentationRegistry.getContext(),
    EventDatabase.class).build();
    eventDao = eventDatabase.eventDao();
    }
    @Test
    public void addEvent_SuccessfullyAddsEvent() throws InterruptedException {
    Event event = generateEventTestData(0, "Wedding");
    eventDao.addEvent(event);
    List eventRetrieved = getValue(eventDao.getEvents(LocalDateTime.now()));
    assertEquals(event.getName(), eventRetrieved.get(0).getName());
    }
    }
    

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50. @RunWith(AndroidJUnit4.class)
    public class EventDaoTest {
    EventDao eventDao;
    EventDatabase eventDatabase;
    @Before
    public void setup() {
    eventDatabase = Room.inMemoryDatabaseBuilder(InstrumentationRegistry.getContext(),
    EventDatabase.class).build();
    eventDao = eventDatabase.eventDao();
    }
    @Test
    public void addEvent_SuccessfullyAddsEvent() throws InterruptedException {
    Event event = generateEventTestData(0, "Wedding");
    eventDao.addEvent(event);
    List eventRetrieved = getValue(eventDao.getEvents(LocalDateTime.now()));
    assertEquals(event.getName(), eventRetrieved.get(0).getName());
    }
    }
    

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51. @RunWith(AndroidJUnit4.class)
    public class EventDaoTest {
    EventDao eventDao;
    EventDatabase eventDatabase;
    @Before
    public void setup() {
    eventDatabase = Room.inMemoryDatabaseBuilder(InstrumentationRegistry.getContext(),
    EventDatabase.class).build();
    eventDao = eventDatabase.eventDao();
    }
    @Test
    public void addEvent_SuccessfullyAddsEvent() throws InterruptedException {
    Event event = generateEventTestData(0, "Wedding");
    eventDao.addEvent(event);
    List eventRetrieved = getValue(eventDao.getEvents(LocalDateTime.now()));
    assertEquals(event.getName(), eventRetrieved.get(0).getName());
    }
    }
    

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52. @RunWith(AndroidJUnit4.class)
    public class EventDaoTest {
    EventDao eventDao;
    EventDatabase eventDatabase;
    @Before
    public void setup() {
    eventDatabase = Room.inMemoryDatabaseBuilder(InstrumentationRegistry.getContext(),
    EventDatabase.class).build();
    eventDao = eventDatabase.eventDao();
    }
    @Test
    public void addEvent_SuccessfullyAddsEvent() throws InterruptedException {
    Event event = generateEventTestData(0, "Wedding");
    eventDao.addEvent(event);
    List eventRetrieved = getValue(eventDao.getEvents(LocalDateTime.now()));
    assertEquals(event.getName(), eventRetrieved.get(0).getName());
    }
    }
    

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53. Testing Models/
    Repositories
    

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54. View
    ViewModel
    Model
    Retrofit API
    Room Database
    Web
    Service
    SQLite
    Model Tests
    

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55. public class EventRepositoryImplTest {
    @Mock
    private EventDao eventDao;
    @Rule
    public InstantTaskExecutorRule instantExecutorRule = new InstantTaskExecutorRule();
    private EventRepository eventRepository;
    @Before
    public void setUp() {
    MockitoAnnotations.initMocks(this);
    eventRepository = new EventRepositoryImpl(eventDao);
    }
    @Test
    public void addEvent_TriggersDbAdd(){
    Event event = FakeEventDataGenerator.getFakeEvent();
    eventRepository.addEvent(event).test().onComplete();
    verify(eventDao).addEvent(event);
    }
    }
    

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56. public class EventRepositoryImplTest {
    @Mock
    private EventDao eventDao;
    @Rule
    public InstantTaskExecutorRule instantExecutorRule = new InstantTaskExecutorRule();
    private EventRepository eventRepository;
    @Before
    public void setUp() {
    MockitoAnnotations.initMocks(this);
    eventRepository = new EventRepositoryImpl(eventDao);
    }
    @Test
    public void addEvent_TriggersDbAdd(){
    Event event = FakeEventDataGenerator.getFakeEvent();
    eventRepository.addEvent(event).test().onComplete();
    verify(eventDao).addEvent(event);
    }
    }
    

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57. public class EventRepositoryImplTest {
    @Mock
    private EventDao eventDao;
    @Rule
    public InstantTaskExecutorRule instantExecutorRule = new InstantTaskExecutorRule();
    private EventRepository eventRepository;
    @Before
    public void setUp() {
    MockitoAnnotations.initMocks(this);
    eventRepository = new EventRepositoryImpl(eventDao);
    }
    @Test
    public void addEvent_TriggersDbAdd(){
    Event event = FakeEventDataGenerator.getFakeEvent();
    eventRepository.addEvent(event).test().onComplete();
    verify(eventDao).addEvent(event);
    }
    }
    

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58. Testing ViewModels
    

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59. View
    ViewModel
    Model
    Retrofit API
    Room Database
    Web
    Service
    SQLite
    View Model Tests
    

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60. public class AddEventViewModelTest {
    AddEventViewModel addEventViewModel;
    @Mock
    EventRepository eventRepository;
    @Rule
    public InstantTaskExecutorRule instantExecutorRule = new InstantTaskExecutorRule();
    @Before
    public void setup() {
    MockitoAnnotations.initMocks(this);
    addEventViewModel = new AddEventViewModel();
    addEventViewModel.eventRepository = eventRepository;
    }
    @Test
    public void addEvent() {
    when(eventRepository.addEvent(any())).thenReturn(Completable.complete());
    addEventViewModel.addEvent();
    verify(eventRepository).addEvent(any());
    }
    

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61. public class AddEventViewModelTest {
    AddEventViewModel addEventViewModel;
    @Mock
    EventRepository eventRepository;
    @Rule
    public InstantTaskExecutorRule instantExecutorRule = new InstantTaskExecutorRule();
    @Before
    public void setup() {
    MockitoAnnotations.initMocks(this);
    addEventViewModel = new AddEventViewModel();
    addEventViewModel.eventRepository = eventRepository;
    }
    @Test
    public void addEvent() {
    when(eventRepository.addEvent(any())).thenReturn(Completable.complete());
    addEventViewModel.addEvent();
    verify(eventRepository).addEvent(any());
    }
    

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62. public class AddEventViewModelTest {
    AddEventViewModel addEventViewModel;
    @Mock
    EventRepository eventRepository;
    @Rule
    public InstantTaskExecutorRule instantExecutorRule = new InstantTaskExecutorRule();
    @Before
    public void setup() {
    MockitoAnnotations.initMocks(this);
    addEventViewModel = new AddEventViewModel();
    addEventViewModel.eventRepository = eventRepository;
    }
    @Test
    public void addEvent() {
    when(eventRepository.addEvent(any())).thenReturn(Completable.complete());
    addEventViewModel.addEvent();
    verify(eventRepository).addEvent(any());
    }
    

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63. View Tests ☕
    

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64. View
    ViewModel
    Model
    Retrofit API
    Room Database
    Web
    Service
    SQLite
    View Tests
    

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65. Espresso Basic Formula
    

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66. @RunWith(AndroidJUnit4.class)
    public class AddEventFragmentTest {
    @Rule
    public ActivityTestRule activityTestRule =
    new ActivityTestRule<>(AddEventActivity.class, true, true);
    private AddEventViewModel addEventViewModel;
    @Before
    public void setup(){
    addEventViewModel = mock(AddEventViewModel.class);
    //..
    }
    @Test
    public void addEvent(){
    when(addEventViewModel.getEventDateTime()).thenReturn(LocalDateTime.now());
    onView(withId(R.id.edit_text_title)).perform(typeText("Christmas Day"),
    closeSoftKeyboard());
    onView(withId(R.id.button_set_date)).perform(click());
    onView(withText("OK")).perform(scrollTo(), click());
    onView(withId(R.id.button_add)).perform(click());
    

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67. public ActivityTestRule activityTestRule =
    new ActivityTestRule<>(AddEventActivity.class, true, true);
    private AddEventViewModel addEventViewModel;
    @Before
    public void setup(){
    addEventViewModel = mock(AddEventViewModel.class);
    //..
    }
    @Test
    public void addEvent(){
    when(addEventViewModel.getEventDateTime()).thenReturn(LocalDateTime.now());
    onView(withId(R.id.edit_text_title)).perform(typeText("Christmas Day"),
    closeSoftKeyboard());
    onView(withId(R.id.button_set_date)).perform(click());
    onView(withText("OK")).perform(scrollTo(), click());
    onView(withId(R.id.button_add)).perform(click());
    }
    }
    

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68. public ActivityTestRule activityTestRule =
    new ActivityTestRule<>(AddEventActivity.class, true, true);
    private AddEventViewModel addEventViewModel;
    @Before
    public void setup(){
    addEventViewModel = mock(AddEventViewModel.class);
    //..
    }
    @Test
    public void addEvent(){
    when(addEventViewModel.getEventDateTime()).thenReturn(LocalDateTime.now());
    onView(withId(R.id.edit_text_title)).perform(typeText("Christmas Day"),
    closeSoftKeyboard());
    onView(withId(R.id.button_set_date)).perform(click());
    onView(withText("OK")).perform(scrollTo(), click());
    onView(withId(R.id.button_add)).perform(click());
    }
    }
    

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69. public ActivityTestRule activityTestRule =
    new ActivityTestRule<>(AddEventActivity.class, true, true);
    private AddEventViewModel addEventViewModel;
    @Before
    public void setup(){
    addEventViewModel = mock(AddEventViewModel.class);
    //..
    }
    @Test
    public void addEvent(){
    when(addEventViewModel.getEventDateTime()).thenReturn(LocalDateTime.now());
    onView(withId(R.id.edit_text_title)).perform(typeText("Christmas Day"),
    closeSoftKeyboard());
    onView(withId(R.id.button_set_date)).perform(click());
    onView(withText("OK")).perform(scrollTo(), click());
    onView(withId(R.id.button_add)).perform(click());
    }
    }
    

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70. Running UI Tests
    

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72. What about Android
    classes or static methods?
    

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73. JUnit tests
    View
    ViewModel
    Repository
    ResourceProvider
    SharedPrefProvider
    MVVM
    

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74. Android Unit tests
    View
    ViewModel
    Repository
    ResourceProvider
    SharedPrefProvider
    MVVM
    

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75. public class ResourceProvider {
    private final Context context;
    public ResourceProvider(Context context){
    this.context = context;
    }
    public String getString(Integer resId){
    return context.getString(resId);
    }
    }
    

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77. Summary
    Encourages
    clean code
    (
    UI Tests
    using Espresso
    
    Less memory
    leaks and bugs
    
    Simplifies code
    
    

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78. @riggaroo
    Thank you!
    developer.android.com/arch
    Rebecca Franks
    @riggaroo
    

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