Testable Android Apps using data binding and MVVM

Fabio Collini

GDG DevFest – Milano – October 2015 – @fabioCollini 2

Ego slide@fabioCollini linkedin.com/in/fabiocollini Folder Organizer cosenonjaviste.it

nana bianca Freapp instal.com Rain tomorrow?

Agenda

1. ROI and Legacy code 2. Model View ViewModel 3. JVM Unit tests 4. Mockito 5. Espresso

GDG DevFest - Milano - October 2015 - @fabioCollini 4

1ROI and legacy code

Quick survey

Do you write automated tests?

Return of Investment - ROI

Net profit Investment

Legacy code

Edit and pray Vs

Cover and modify

Legacy code is code without unit tests

Test After Development

Write the feature implementation Do some manual testing Try to write automatic tests Modify the initial implementation to test it

“Standard” Android code is not testable :(

Legacy code dilemma

When we change code, we should have tests in place.

To put tests in place, we often have to change code.

Michael Feathers

2Model View ViewModel

Testable code

Data binding and MVVM

Model View ViewModel

ViewModel

DataBinding

Android Model View ViewModel

ViewModel

DataBinding

Retained on configuration change

Saved in Activity or Fragment state

Activity or Fragment

https://github.com/fabioCollini/mv2m

NoteActivity

NoteViewModel

NoteModel

note_detail.xml NoteDetailBinding

DataBinding

View ViewModel RetrofitService

onClick

updatebinding

View ViewModel RetrofitServiceModel

request

response

binding

NoteModel

Saved on Activity state

public class NoteModel implements Parcelable { private long noteId; private ObservableBoolean error = new ObservableBoolean(); private ObservableString title = new ObservableString(); private ObservableString text = new ObservableString(); private ObservableInt titleError = new ObservableInt(); private ObservableInt textError = new ObservableInt(); //...}

NoteActivity

public class NoteActivity extends ViewModelActivity<NoteViewModel> { @Override public NoteViewModel createViewModel() { return new NoteViewModel(/* .. */); } @Override protected void onCreate(Bundle state) { super.onCreate(state); NoteDetailBinding binding = DataBindingUtil.setContentView(this, R.layout.note_detail); binding.setViewModel(viewModel); } }

note_detail.xml<?xml version="1.0" encoding="utf-8"?> <layout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto"> <data> <variable name="viewModel" type="it.cosenonjaviste.core.NoteViewModel"/> </data> <FrameLayout android:layout_width="match_parent" android:layout_height="match_parent">  </FrameLayout> </layout>

note_detail.xml<LinearLayout app:visible="@{viewModel.loading}">

note_detail.xml<LinearLayout> <android.support.design.widget.TextInputLayout app:error=“@{viewModel.model.titleError}"> <EditText app:binding=“@{viewModel.model.title}" /> </android.support.design.widget.TextInputLayout>

<RelativeLayout> <Button android:enabled="@{!viewModel.sending}" app:onClick="@{viewModel.save}"/>

</RelativeLayout> </LinearLayout>

app:binding

@BindingAdapter({"app:binding"})public static void bindEditText(EditText view, final ObservableString observableString) { if (view.getTag(R.id.binded) == null) { view.setTag(R.id.binded, true); view.addTextChangedListener(new TextWatcherAdapter() { @Override public void onTextChanged( CharSequence s, int st, int b, int c) { observableString.set(s.toString()); } }); } String newValue = observableString.get(); if (!view.getText().toString().equals(newValue)) { view.setText(newValue); }}

app:visible app:onClick

@BindingAdapter({"app:visible"})public static void bindVisible(View view, boolean b) { view.setVisibility(b ? View.VISIBLE : View.INVISIBLE); } @BindingAdapter({"app:onClick"})public static void bindOnClick(View view, final Runnable listener) { view.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { listener.run(); } });}

NoteViewModelpublic class NoteViewModel extends ViewModel<NoteModel> { //... @Override public NoteModel createDefaultModel() { return new NoteModel(); } @Override public void resume() { if (!getModel().isLoaded()) { reloadData(); } } public void reloadData() { } //...}

3JVM Unit tests

Instrumentation tests run on a device (real or emulated)

high code coverage

Vs JVM tests

fast low code coverage

GDG DevFest – Milano – October 2015 – @fabioCollini

JVM Test

NoteActivity

NoteViewModel

NoteModel

note_detail.xml NoteDetailBinding

DataBinding

NoteViewModel.reloadDatapublic class NoteViewModel extends ViewModel<NoteModel> { //...

@Override public void resume() { if (!getModel().isLoaded()) { reloadData(); } } public void reloadData() { try { Note note = NoteLoader.singleton().load(); getModel().update(note); } catch (Exception e) { getModel().getError().set(true); } } //...}

First test

AssertJ

@Testpublic void testLoadData() { NoteViewModel viewModel = new NoteViewModel(); NoteModel model = viewModel.initAndResume(); assertThat(model.getTitle().get()).isEqualTo("???"); assertThat(model.getText().get()).isEqualTo("???"); assertThat(model.getError().get()).isFalse(); }

NoteLoader.singletonpublic class NoteViewModel extends ViewModel<NoteModel> { //...

@Override public void resume() { if (!getModel().isLoaded()) { reloadData(); } } public void reloadData() { try { Note note = NoteLoader.singleton().load(); getModel().update(note); } catch (Exception e) { getModel().getError().set(true); } } //...}

Dependency Injectionpublic class NoteViewModel extends ViewModel<NoteModel, NoteView> {

private NoteLoader noteLoader;

public NoteViewModel(NoteLoader noteLoader) { this.noteLoader = noteLoader; } public void reloadData() { try { Note note = noteLoader.load(); getModel().update(note); } catch (Exception e) { getModel().getError().set(true); } } //... }

NoteLoaderStub

public class NoteLoaderStub implements NoteLoader { private Note note; public NoteLoaderStub(Note note) { this.note = note; } @Override public Note load() { return note; } }

Test with stub

@Testpublic void testLoadData() { NoteLoaderStub stub = new NoteLoaderStub(new Note(1, "a", "b")); NoteViewModel viewModel = new NoteViewModel(stub); NoteModel model = viewModel.initAndResume(); assertThat(model.getTitle().get()).isEqualTo("a"); assertThat(model.getText().get()).isEqualTo("b"); assertThat(model.getError().get()).isFalse(); }

public void save() { NoteModel model = getModel(); boolean titleValid = checkMandatory( model.getTitle(), model.getTitleError()); boolean textValid = checkMandatory( model.getText(), model.getTextError()); if (titleValid && textValid) { try { noteSaver.save( model.getNoteId(), model.getTitle().get(), model.getText().get());

messageManager.showMessage(R.string.note_saved); } catch (RetrofitError e) { messageManager.showMessage( R.string.error_saving_note); } }}

save method

Dependency Injection

SnackbarMessageManager

public class SnackbarMessageManager implements MessageManager { private Activity activity; @Override public void showMessage(int message) { if (activity != null) { Snackbar.make( activity.findViewById(android.R.id.content), message, Snackbar.LENGTH_LONG ).show(); } } @Override public void setActivity(Activity activity) { this.activity = activity; }}

MessageManagerSpy

public class MessageManagerSpy implements MessageManager { public int message; @Override public void showMessage(int message) { this.message = message; } @Override public void setActivity(Activity activity) { }}

NoteSaverSpy

public class NoteSaverSpy implements NoteSaver { public long id; public String title; public String text; @Override public Response save( long id, String title, String text) { this.id = id; this.title = title; this.text = text; return null; } }

Test with spy@Testpublic void testSaveData() { NoteLoaderStub stub = new NoteLoaderStub(new Note(1, "a", "b")); NoteSaverSpy saverSpy = new NoteSaverSpy(); MessageManagerSpy messageSpy = new MessageManagerSpy(); NoteViewModel viewModel = new NoteViewModel( stub, saverSpy, messageSpy); NoteModel model = viewModel.initAndResume(); model.getTitle().set("newTitle"); model.getText().set("newText"); viewModel.save(); assertThat(saverSpy.id).isEqualTo(1L); assertThat(saverSpy.title).isEqualTo("newTitle"); assertThat(saverSpy.text).isEqualTo("newText"); assertThat(messageSpy.message) .isEqualTo(R.string.note_saved); }

4Mockito

Mockito@Testpublic void testLoadData() { NoteLoader noteLoader = Mockito.mock(NoteLoader.class); NoteSaver noteSaver = Mockito.mock(NoteSaver.class); MessageManager messageManager = Mockito.mock(MessageManager.class); NoteViewModel viewModel = new NoteViewModel( noteLoader, noteSaver, messageManager); when(noteLoader.load()) .thenReturn(new Note(123, "title", "text"));

NoteModel model = viewModel.initAndResume(); assertThat(model.getTitle().get()).isEqualTo("title"); assertThat(model.getText().get()).isEqualTo("text"); }

MockLoader

MockLoaderNoteLoader

NoteLoader

ViewModel

initAndResume

update

request

response

JVM Test

ViewModel ModelJVM Test

assert

when().thenReturn()

Mockito@Testpublic void testSaveData() { //... NoteModel model = viewModel.initAndResume(); model.getTitle().set("newTitle"); model.getText().set("newText"); viewModel.save(); verify(noteSaver) .save(eq(123L), eq("newTitle"), eq("newText")); verify(messageManager) .showMessage(eq(R.string.note_saved)); }

MockMessage ManagerMessage Manager

ViewModel MockSaver

showMessage

request

response

JVM Test

ViewModel MockSaverModelJVM Test

verify

NoteSaver

SetUp method public class NoteViewModelTest { private NoteLoader noteLoader; private NoteSaver noteSaver; private MessageManager messageManager; private NoteViewModel viewModel; @Before public void setUp() { noteLoader = Mockito.mock(NoteLoader.class); noteSaver = Mockito.mock(NoteSaver.class); messageManager = Mockito.mock(MessageManager.class); viewModel = new NoteViewModel( noteLoader, noteSaver, messageManager);

when(noteLoader.load()) .thenReturn(new Note(123, "title", "text")); } //...}

@Mock and @InjectMocks@RunWith(MockitoJUnitRunner.class) public class NoteViewModelTest { @Mock NoteLoader noteLoader; @Mock NoteSaver noteSaver; @Mock MessageManager messageManager; @InjectMocks NoteViewModel viewModel; @Before public void setUp() throws Exception { when(noteLoader.load()) .thenReturn(new Note(123, "title", "text")); } //...}

Dagger

A fast dependency injector for Android and Java v1 developed at Square https://github.com/square/dagger

v2 developed at Google https://github.com/google/dagger

Configuration using annotations and Java classes Based on annotation processing (no reflection)

Background executor

if (titleValid && textValid) { sending.set(true); backgroundExecutor.execute(new Runnable() { @Override public void run() { try { noteSaver.save(getModel().getNoteId(), getModel().getTitle().get(), getModel().getText().get()); hideSendProgressAndShowMessage( R.string.note_saved); } catch (RetrofitError e) { hideSendProgressAndShowMessage( R.string.error_saving_note); } } }); }

Ui Executor

private void hideSendProgressAndShowMessage(final int msg) { uiExecutor.execute(new Runnable() { @Override public void run() { messageManager.showMessage(msg); sending.set(false); } }); }

Test using single thread@RunWith(MockitoJUnitRunner.class) public class NoteViewModelTest { @Mock NoteView view; @Mock NoteLoader noteLoader; @Mock NoteSaver noteSaver; @Spy Executor executor = new Executor() { @Override public void execute(Runnable command) { command.run(); } }; @InjectMocks NoteViewModel viewModel; //...}

5Espresso

NoteLoaderpublic class NoteLoader { private static NoteLoader instance; public static NoteLoader singleton() { if (instance == null) { instance = new NoteLoader(); } return instance; } private NoteLoader() { } @VisibleForTesting public static void setInstance(NoteLoader instance) { NoteLoader.instance = instance; } //...}

public class NoteActivityTest { @Rule public ActivityTestRule<NoteActivity> rule = new ActivityTestRule<>(NoteActivity.class, false, false); private NoteLoader noteLoader; @Before public void setUp() throws Exception { noteLoader = Mockito.mock(NoteLoader.class); NoteLoader.setInstance(noteLoader); }

//...}

NoteActivityTest

Reload test@Testpublic void testReloadAfterError() { when(noteLoader.load()) .thenThrow( RetrofitError.networkError("url", new IOException())) .thenReturn(new Note(123, "aaa", "bbb")); rule.launchActivity(null); onView(withText(R.string.retry)).perform(click()); onView(withText(“aaa")) .check(matches(isDisplayed())); onView(withText(“bbb")) .check(matches(isDisplayed())); }

View ViewModel MockLoader

perform(click())

updatebinding

requestresponse

EspressoTest

View ViewModel MockLoaderModelEspressoTest

onView

verify

NoteLoader

when().thenReturn()

onClickbinding

Android Model View ViewModel

Activity (or Fragment) is the View All the business logic is in the ViewModel ViewModel is managed using Dependency Injection Model is the Activity (or Fragment) state ViewModel is retained on configuration change ViewModel is testable using a JVM test

mockito.org joel-costigliola.github.io/assertj

Jay Fields - Working Effectively with Unit Tests Michael Feathers - Working Effectively with Legacy Code

medium.com/@fabioCollini/android-data-binding-f9f9d3afc761

github.com/fabioCollini/mv2m github.com/commit-non-javisti/CoseNonJavisteAndroidApp

Thanks for your attention!

androidavanzato.it

Questions?

Testable Android Apps using data binding and MVVM

Software

Adopting MVVM

MVVM w Android - Poznań University of Technology...MVVM w Android KONWENCJA ORGANIZACJI PROJEKTU I DATA BINDING LIBRARY Składowe aplikacji Activity Activities stanowią „widoki”

ReactiveUI: Rx + MVVM

MVVM DesignPatterns

Programming with MVVM

Microsoft and Mobile - Meetupfiles.meetup.com/1698110/MicrosoftMobileIntro - Marsman.pdf• MVVM Pattern with Data Binding (to abstract logic from UI) • Linked files • #if conditionals

MVVM & RxSwift

Advanced MVVM

WPF MVVM Toolkit

MVVM on iOS

Protocol-Oriented MVVM

MVVM Cross

Mvvm crossevent basics

Pattern MVVM avec MVVM Light Toolkit

Xamarin Data Binding MVVM Patternapm/CMSW/docs/16XamMVVM.pdf · 2018-12-03 · Xamarin Data Binding MVVM Pattern. ... User interactions in the form of a click or tap gesture trigger

KnockoutJS and MVVM

MVVM Lights

Training: MVVM Pattern

Mvvm basics

KendoUI MVVM