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Writing testable android apps

K
K. Matthew Dupree

The document discusses how to write testable code through the use of seams. It explains that seams allow code to be altered without changing the code itself, improving testability. Dependency injection creates object seams by decoupling classes, and model-view-presenter architecture leverages this. Build variants introduce link seams. Without seams, it can be difficult to arrange objects and assert outcomes in tests. Examples show refactoring code to introduce seams, like using interfaces, which allows dependencies to be mocked and behavior verified.

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Writing testable android apps
Writing Testable Apps
Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
Why tests?
Why tests?
Why are we here?
“the goal of software delivery is to sustainably minimize the lead time to business impact”
Yes, but why tests?
–Steve Freeman and Nat Pryce, authors of Growing Object Oriented Software Guided by Tests “for a class to be easy to unit-test, the class must…be loosely coupled and highly cohesive —in other words, well-designed.”
“We invest in this huge testing framework… engineers here have the power to try out an idea and ship it to maybe 10,000 people or 100,000 people.”
Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
–Michael Feathers, Working Effectively with Legacy Code “One of the things that nearly everyone notices when they try to write tests for existing code is just how poorly suited code is to testing.”
Writing testable android apps
Writing testable android apps
Writing testable android apps
public class PresenterFragmentImpl extends Fragment implements Presenter, UpdatableView.UserActionListener, LoaderManager.LoaderCallbacks<Cursor> { @Override public Loader<Cursor> onCreateLoader(int id, Bundle args) { Loader<Cursor> cursorLoader = createLoader(id, args); mLoaderIdlingResource.onLoaderStarted(cursorLoader); return cursorLoader; } @Override public void onLoadFinished(Loader<Cursor> loader, Cursor data) { processData(loader, data); mLoaderIdlingResource.onLoaderFinished(loader); } }
public class PresenterFragmentImpl extends Fragment implements Presenter, UpdatableView.UserActionListener, LoaderManager.LoaderCallbacks<Cursor> { @Override public Loader<Cursor> onCreateLoader(int id, Bundle args) { Loader<Cursor> cursorLoader = createLoader(id, args); mLoaderIdlingResource.onLoaderStarted(cursorLoader); return cursorLoader; } @Override public void onLoadFinished(Loader<Cursor> loader, Cursor data) { processData(loader, data); mLoaderIdlingResource.onLoaderFinished(loader); } }
What makes code testable?
Writing testable android apps
@Override public void onSharedPreferenceChanged(SharedPreferences sharedPrefs, String key) { if (SettingsUtils.PREF_SYNC_CALENDAR.equals(key)) { Intent intent; if (SettingsUtils.shouldSyncCalendar(getActivity())) { // Add all calendar entries intent = new Intent(ACTION_UPDATE_ALL_SESSIONS_CALENDAR); } else { // Remove all calendar entries intent = new Intent(ACTION_CLEAR_ALL_SESSIONS_CALENDAR); } intent.setClass(getActivity(), SessionCalendarService.class); getActivity().startService(intent); } }
@Override public void onSharedPreferenceChanged(SharedPreferences sharedPrefs, String key) { if (SettingsUtils.PREF_SYNC_CALENDAR.equals(key)) { Intent intent; if (SettingsUtils.shouldSyncCalendar(getActivity())) { // Add all calendar entries intent = new Intent(ACTION_UPDATE_ALL_SESSIONS_CALENDAR); } else { // Remove all calendar entries intent = new Intent(ACTION_CLEAR_ALL_SESSIONS_CALENDAR); } intent.setClass(getActivity(), SessionCalendarService.class); getActivity().startService(intent); } }
@Override public void onSharedPreferenceChanged(SharedPreferences sharedPrefs, String key) { if (SettingsUtils.PREF_SYNC_CALENDAR.equals(key)) { Intent intent; if (SettingsUtils.shouldSyncCalendar(getActivity())) { // Add all calendar entries intent = new Intent(ACTION_UPDATE_ALL_SESSIONS_CALENDAR); } else { // Remove all calendar entries intent = new Intent(ACTION_CLEAR_ALL_SESSIONS_CALENDAR); } intent.setClass(getActivity(), SessionCalendarService.class); getActivity().startService(intent); } }
@Test public void onSPChangedRemovesSessions() throws Exception { // Arrange //Act mSettingsFragment.onSPChanged(mMockSharedPreferences, PREF_SYNC_CALENDAR); //Assert }
@Test public void onSPChangedRemovesSessions() throws Exception { // Arrange //Act mSettingsFragment.onSPChanged(mMockSharedPreferences, PREF_SYNC_CALENDAR); //Assert }
@Override public void onSharedPreferenceChanged(SharedPreferences sharedPrefs, String key) { if (SettingsUtils.PREF_SYNC_CALENDAR.equals(key)) { Intent intent; if (SettingsUtils.shouldSyncCalendar(getActivity())) { // Add all calendar entries intent = new Intent(ACTION_UPDATE_ALL_SESSIONS_CALENDAR); } else { // Remove all calendar entries intent = new Intent(ACTION_CLEAR_ALL_SESSIONS_CALENDAR); } intent.setClass(getActivity(), SessionCalendarService.class); getActivity().startService(intent); } }
@Test public void onSPChangedRemovesSessions() throws Exception { // Arrange //Act mSettingsFragment.onSPChanged(mMockSharedPreferences, PREF_SYNC_CALENDAR); //Assert }
@Override public void onSharedPreferenceChanged(SharedPreferences sharedPrefs, String key) { if (SettingsUtils.PREF_SYNC_CALENDAR.equals(key)) { Intent intent; if (SettingsUtils.shouldSyncCalendar(getActivity())) { // Add all calendar entries intent = new Intent(ACTION_UPDATE_ALL_SESSIONS_CALENDAR); } else { // Remove all calendar entries intent = new Intent(ACTION_CLEAR_ALL_SESSIONS_CALENDAR); } intent.setClass(getActivity(), SessionCalendarService.class); getActivity().startService(intent); } }
Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
Writing testable android apps
–Michael Feathers, author of Working Effectively with Legacy Code “A seam is a place where you can alter behavior in your program without editing in that place.”
Without seams, it’s often difficult to arrange and/or assert
Writing testable android apps
class CalendarUpdatingOnSharedPreferenceChangedListener { void onPreferenceChanged(CalendarPreferences calendarPreferences, String key) { if (SettingsUtils.PREF_SYNC_CALENDAR.equals(key)) { if (calendarPreferences.shouldSyncCalendar()) { mSessUpdaterLauncher.launchAddAllSessionsUpdater(); } else { mSessUpdaterLauncher.launchClearAllSessionsUpdate(); } } } }
class CalendarUpdatingOnSharedPreferenceChangedListener { void onPreferenceChanged(CalendarPreferences calendarPreferences, String key) { if (SettingsUtils.PREF_SYNC_CALENDAR.equals(key)) { if (calendarPreferences.shouldSyncCalendar()) { mSessUpdaterLauncher.launchAddAllSessionsUpdater(); } else { mSessUpdaterLauncher.launchClearAllSessionsUpdate(); } } } }
class CalendarUpdatingOnSharedPreferenceChangedListener { void onPreferenceChanged(CalendarPreferences calendarPreferences, String key) { if (SettingsUtils.PREF_SYNC_CALENDAR.equals(key)) { if (calendarPreferences.shouldSyncCalendar()) { mSessUpdaterLauncher.launchAddAllSessionsUpdater(); } else { mSessUpdaterLauncher.launchClearAllSessionsUpdate(); } } } }
class CalendarUpdatingOnSharedPreferenceChangedListener { void onPreferenceChanged(CalendarPreferences calendarPreferences, String key) { if (SettingsUtils.PREF_SYNC_CALENDAR.equals(key)) { if (calendarPreferences.shouldSyncCalendar()) { mSessUpdaterLauncher.launchAddAllSessionsUpdater(); } else { mSessUpdaterLauncher.launchClearAllSessionsUpdate(); } } } }
@Test public void onPreferenceChangedClearedCalendar() throws Exception { // Arrange CUOSPCListener listener = new CUOSPCListener(mSessionUpdateLauncher); final CalendarPreferences calendarPreferences = mock(CalendarPreferences.class); when(calendarPreferences.shouldSyncCalendar()).thenReturn(false); // Act listener.onPreferenceChanged(calendarPreferences, SettingsUtils.PREF_SYNC_CALENDAR); // Assert verify(mSessionUpdateLauncher).launchClearAllSessionsUpdate(); }
@Test public void onPreferenceChangedClearedCalendar() throws Exception { // Arrange CUOSPCListener listener = new CUOSPCListener(mSessionUpdateLauncher); final CalendarPreferences calendarPreferences = mock(CalendarPreferences.class); when(calendarPreferences.shouldSyncCalendar()).thenReturn(false); // Act listener.onPreferenceChanged(calendarPreferences, SettingsUtils.PREF_SYNC_CALENDAR); // Assert verify(mSessionUpdateLauncher).launchClearAllSessionsUpdate(); }
@Test public void onPreferenceChangedClearedCalendar() throws Exception { // Arrange CUOSPCListener listener = new CUOSPCListener(mSessionUpdateLauncher); final CalendarPreferences calendarPreferences = mock(CalendarPreferences.class); when(calendarPreferences.shouldSyncCalendar()).thenReturn(false); // Act listener.onPreferenceChanged(calendarPreferences, SettingsUtils.PREF_SYNC_CALENDAR); // Assert verify(mSessionUpdateLauncher).launchClearAllSessionsUpdate(); }
class CalendarUpdatingOnSharedPreferenceChangedListener { void onPreferenceChanged(CalendarPreferences calendarPreferences, String key) { if (SettingsUtils.PREF_SYNC_CALENDAR.equals(key)) { if (calendarPreferences.shouldSyncCalendar()) { mSessUpdaterLauncher.launchAddAllSessionsUpdater(); } else { mSessUpdaterLauncher.launchClearAllSessionsUpdate(); } } } }
Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
Object Seams
–Michael Feathers “The fundamental thing to recognize is that when we look at a call in an object-oriented program, it does not define which method will actually be executed.”
DI != Dagger
The code that needs dependencies is not responsible for getting them
Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
Writing testable android apps
private void setupCards(CollectionView.Inventory inventory) { if (SettingsUtils.isAttendeeAtVenue(getContext())) { if (!hasAnsweredConfMessageCardsPrompt(getContext())) { inventoryGroup = new InventoryGroup(GROUP_ID_MESSAGE_CARDS); MessageData conferenceMessageOptIn = MessageCardHelper .getConferenceOptInMessageData(getContext()); inventoryGroup.addItemWithTag(conferenceMessageOptIn); inventoryGroup.setDisplayCols(1); inventory.addGroup(inventoryGroup); } // ... } }
private void setupCards(CollectionView.Inventory inventory) { if (SettingsUtils.isAttendeeAtVenue(getContext())) { if (!hasAnsweredConfMessageCardsPrompt(getContext())) { inventoryGroup = new InventoryGroup(GROUP_ID_MESSAGE_CARDS); MessageData conferenceMessageOptIn = MessageCardHelper .getConferenceOptInMessageData(getContext()); inventoryGroup.addItemWithTag(conferenceMessageOptIn); inventoryGroup.setDisplayCols(1); inventory.addGroup(inventoryGroup); } // ... } }
private void setupCards(CollectionView.Inventory inventory) { if (SettingsUtils.isAttendeeAtVenue(getContext())) { if (!hasAnsweredConfMessageCardsPrompt(getContext())) { inventoryGroup = new InventoryGroup(GROUP_ID_MESSAGE_CARDS); MessageData conferenceMessageOptIn = MessageCardHelper .getConferenceOptInMessageData(getContext()); inventoryGroup.addItemWithTag(conferenceMessageOptIn); inventoryGroup.setDisplayCols(1); inventory.addGroup(inventoryGroup); } // ... } }
class Presenter { public void presentCards() { if (mIsAttendeeAtVenue) { if (!mMsgSettings.hasAnsweredMessagePrompt()) { mExploreView.addMessageOptInCard(); } // Stuff } } }
class Presenter { public void presentCards() { if (mIsAttendeeAtVenue) { if (!mMsgSettings.hasAnsweredMessagePrompt()) { mExploreView.addMessageOptInCard(); } // Stuff } } }
class Presenter { public void presentCards() { if (mIsAttendeeAtVenue) { if (!mMsgSettings.hasAnsweredMessagePrompt()) { mExploreView.addMessageOptInCard(); } // Stuff } } }
class Presenter { public void presentCards() { if (mIsAttendeeAtVenue) { if (!mMsgSettings.hasAnsweredMessagePrompt()) { mExploreView.addMessageOptInCard(); } // Stuff } } }
Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
–Michael Feathers “[code] contains calls to code in other files. Linkers…resolve each of the calls so that you can have a complete program at runtime…you can usually exploit [this] to substitute pieces of your program”
Use Link Seams for Espresso Tests
Writing testable android apps
Writing testable android apps
public class PresenterFragmentImpl extends Fragment implements Presenter, UpdatableView.UserActionListener, LoaderManager.LoaderCallbacks<Cursor> { @Override public Loader<Cursor> onCreateLoader(int id, Bundle args) { Loader<Cursor> cursorLoader = createLoader(id, args); mLoaderIdlingResource.onLoaderStarted(cursorLoader); return cursorLoader; } @Override public void onLoadFinished(Loader<Cursor> loader, Cursor data) { processData(loader, data); mLoaderIdlingResource.onLoaderFinished(loader); } }
public class PresenterFragmentImpl extends Fragment implements Presenter, UpdatableView.UserActionListener, LoaderManager.LoaderCallbacks<Cursor> { @Override public Loader<Cursor> onCreateLoader(int id, Bundle args) { Loader<Cursor> cursorLoader = createLoader(id, args); mLoaderIdlingResource.onLoaderStarted(cursorLoader); return cursorLoader; } @Override public void onLoadFinished(Loader<Cursor> loader, Cursor data) { processData(loader, data); mLoaderIdlingResource.onLoaderFinished(loader); } }
public PresenterFragmentImpl addPresenterFragment(int uVResId, Model model, QueryEnum[] queries, UserActionEnum[] actions){ //... if (presenter == null) { //Create, set up and add the presenter. presenter = new PresenterFragmentImpl(); //... } else { //... } return presenter; }
public PresenterFragmentImpl addPresenterFragment(int uVResId, Model model, QueryEnum[] queries, UserActionEnum[] actions){ //... if (presenter == null) { //Create, set up and add the presenter. presenter = new PresenterFragmentImpl(); //... } else { //... } return presenter; }
Writing testable android apps
Writing testable android apps
flavorDimensions 'datasource', 'features' productFlavors { mock { dimension 'datasource' } prod { dimension 'datasource' } free { dimension 'features' } }
Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
More complicated object graphs can lead to…
Writing testable android apps
Use Link Seams to swap out factories so you can use object seams
Use Link Seams to swap out factories so you can use object seams
public class FragFactory { public PresenterFragmentImpl make() { return new PresenterFragmentImpl(); } } public class FragFactory { public PresenterFragmentImpl make() { return new MockPresenterFragmentImpl(); } }
public class FragFactory { public PresenterFragmentImpl make() { return new PresenterFragmentImpl(); } } public class FragFactory { public PresenterFragmentImpl make() { return new MockPresenterFragmentImpl(); } }
public class FragFactory { public PresenterFragmentImpl make() { return new PresenterFragmentImpl(); } } public class FragFactory { public PresenterFragmentImpl make() { return new MockPresenterFragmentImpl(); } }
public PresenterFragmentImpl addPresenterFragment(int uVResId, Model model, QueryEnum[] queries, UserActionEnum[] actions){ //... if (presenter == null) { //Create, set up and add the presenter. presenter = new PresenterFragmentImpl(); // 1 seam //... } else { //... } return presenter; }
public PresenterFragmentImpl addPresenterFragment(int uVResId, Model model, QueryEnum[] queries, UserActionEnum[] actions){ //... if (presenter == null) { //Create, set up and add the presenter. presenter = mFragFactory.make(); // 2 seams //... } else { //... } return presenter; }
This second seam buys you “mock mode”
Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
Writing Testable Apps
• “Microservices: Software That Fits in Your Head” • “Mark Zuckerberg: How to Build the Future” • Growing Object Oriented Software Guided by Tests • Working Effectively with Legacy Code • “Dependency Injection” by Martin Fowler • “Android Apps with Dagger” by Jake Wharton Sources

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Writing testable android apps

  • 3. Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
  • 4. Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
  • 7. Why are we here?
  • 8. “the goal of software delivery is to sustainably minimize the lead time to business impact”
  • 9. Yes, but why tests?
  • 10. –Steve Freeman and Nat Pryce, authors of Growing Object Oriented Software Guided by Tests “for a class to be easy to unit-test, the class must…be loosely coupled and highly cohesive —in other words, well-designed.”
  • 11. “We invest in this huge testing framework… engineers here have the power to try out an idea and ship it to maybe 10,000 people or 100,000 people.”
  • 12. Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
  • 13. Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
  • 14. –Michael Feathers, Working Effectively with Legacy Code “One of the things that nearly everyone notices when they try to write tests for existing code is just how poorly suited code is to testing.”
  • 18. public class PresenterFragmentImpl extends Fragment implements Presenter, UpdatableView.UserActionListener, LoaderManager.LoaderCallbacks<Cursor> { @Override public Loader<Cursor> onCreateLoader(int id, Bundle args) { Loader<Cursor> cursorLoader = createLoader(id, args); mLoaderIdlingResource.onLoaderStarted(cursorLoader); return cursorLoader; } @Override public void onLoadFinished(Loader<Cursor> loader, Cursor data) { processData(loader, data); mLoaderIdlingResource.onLoaderFinished(loader); } }
  • 19. public class PresenterFragmentImpl extends Fragment implements Presenter, UpdatableView.UserActionListener, LoaderManager.LoaderCallbacks<Cursor> { @Override public Loader<Cursor> onCreateLoader(int id, Bundle args) { Loader<Cursor> cursorLoader = createLoader(id, args); mLoaderIdlingResource.onLoaderStarted(cursorLoader); return cursorLoader; } @Override public void onLoadFinished(Loader<Cursor> loader, Cursor data) { processData(loader, data); mLoaderIdlingResource.onLoaderFinished(loader); } }
  • 22. @Override public void onSharedPreferenceChanged(SharedPreferences sharedPrefs, String key) { if (SettingsUtils.PREF_SYNC_CALENDAR.equals(key)) { Intent intent; if (SettingsUtils.shouldSyncCalendar(getActivity())) { // Add all calendar entries intent = new Intent(ACTION_UPDATE_ALL_SESSIONS_CALENDAR); } else { // Remove all calendar entries intent = new Intent(ACTION_CLEAR_ALL_SESSIONS_CALENDAR); } intent.setClass(getActivity(), SessionCalendarService.class); getActivity().startService(intent); } }
  • 23. @Override public void onSharedPreferenceChanged(SharedPreferences sharedPrefs, String key) { if (SettingsUtils.PREF_SYNC_CALENDAR.equals(key)) { Intent intent; if (SettingsUtils.shouldSyncCalendar(getActivity())) { // Add all calendar entries intent = new Intent(ACTION_UPDATE_ALL_SESSIONS_CALENDAR); } else { // Remove all calendar entries intent = new Intent(ACTION_CLEAR_ALL_SESSIONS_CALENDAR); } intent.setClass(getActivity(), SessionCalendarService.class); getActivity().startService(intent); } }
  • 24. @Override public void onSharedPreferenceChanged(SharedPreferences sharedPrefs, String key) { if (SettingsUtils.PREF_SYNC_CALENDAR.equals(key)) { Intent intent; if (SettingsUtils.shouldSyncCalendar(getActivity())) { // Add all calendar entries intent = new Intent(ACTION_UPDATE_ALL_SESSIONS_CALENDAR); } else { // Remove all calendar entries intent = new Intent(ACTION_CLEAR_ALL_SESSIONS_CALENDAR); } intent.setClass(getActivity(), SessionCalendarService.class); getActivity().startService(intent); } }
  • 25. @Test public void onSPChangedRemovesSessions() throws Exception { // Arrange //Act mSettingsFragment.onSPChanged(mMockSharedPreferences, PREF_SYNC_CALENDAR); //Assert }
  • 26. @Test public void onSPChangedRemovesSessions() throws Exception { // Arrange //Act mSettingsFragment.onSPChanged(mMockSharedPreferences, PREF_SYNC_CALENDAR); //Assert }
  • 27. @Override public void onSharedPreferenceChanged(SharedPreferences sharedPrefs, String key) { if (SettingsUtils.PREF_SYNC_CALENDAR.equals(key)) { Intent intent; if (SettingsUtils.shouldSyncCalendar(getActivity())) { // Add all calendar entries intent = new Intent(ACTION_UPDATE_ALL_SESSIONS_CALENDAR); } else { // Remove all calendar entries intent = new Intent(ACTION_CLEAR_ALL_SESSIONS_CALENDAR); } intent.setClass(getActivity(), SessionCalendarService.class); getActivity().startService(intent); } }
  • 28. @Test public void onSPChangedRemovesSessions() throws Exception { // Arrange //Act mSettingsFragment.onSPChanged(mMockSharedPreferences, PREF_SYNC_CALENDAR); //Assert }
  • 29. @Override public void onSharedPreferenceChanged(SharedPreferences sharedPrefs, String key) { if (SettingsUtils.PREF_SYNC_CALENDAR.equals(key)) { Intent intent; if (SettingsUtils.shouldSyncCalendar(getActivity())) { // Add all calendar entries intent = new Intent(ACTION_UPDATE_ALL_SESSIONS_CALENDAR); } else { // Remove all calendar entries intent = new Intent(ACTION_CLEAR_ALL_SESSIONS_CALENDAR); } intent.setClass(getActivity(), SessionCalendarService.class); getActivity().startService(intent); } }
  • 30. Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
  • 31. Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
  • 33. –Michael Feathers, author of Working Effectively with Legacy Code “A seam is a place where you can alter behavior in your program without editing in that place.”
  • 34. Without seams, it’s often difficult to arrange and/or assert
  • 36. class CalendarUpdatingOnSharedPreferenceChangedListener { void onPreferenceChanged(CalendarPreferences calendarPreferences, String key) { if (SettingsUtils.PREF_SYNC_CALENDAR.equals(key)) { if (calendarPreferences.shouldSyncCalendar()) { mSessUpdaterLauncher.launchAddAllSessionsUpdater(); } else { mSessUpdaterLauncher.launchClearAllSessionsUpdate(); } } } }
  • 37. class CalendarUpdatingOnSharedPreferenceChangedListener { void onPreferenceChanged(CalendarPreferences calendarPreferences, String key) { if (SettingsUtils.PREF_SYNC_CALENDAR.equals(key)) { if (calendarPreferences.shouldSyncCalendar()) { mSessUpdaterLauncher.launchAddAllSessionsUpdater(); } else { mSessUpdaterLauncher.launchClearAllSessionsUpdate(); } } } }
  • 38. class CalendarUpdatingOnSharedPreferenceChangedListener { void onPreferenceChanged(CalendarPreferences calendarPreferences, String key) { if (SettingsUtils.PREF_SYNC_CALENDAR.equals(key)) { if (calendarPreferences.shouldSyncCalendar()) { mSessUpdaterLauncher.launchAddAllSessionsUpdater(); } else { mSessUpdaterLauncher.launchClearAllSessionsUpdate(); } } } }
  • 39. class CalendarUpdatingOnSharedPreferenceChangedListener { void onPreferenceChanged(CalendarPreferences calendarPreferences, String key) { if (SettingsUtils.PREF_SYNC_CALENDAR.equals(key)) { if (calendarPreferences.shouldSyncCalendar()) { mSessUpdaterLauncher.launchAddAllSessionsUpdater(); } else { mSessUpdaterLauncher.launchClearAllSessionsUpdate(); } } } }
  • 40. @Test public void onPreferenceChangedClearedCalendar() throws Exception { // Arrange CUOSPCListener listener = new CUOSPCListener(mSessionUpdateLauncher); final CalendarPreferences calendarPreferences = mock(CalendarPreferences.class); when(calendarPreferences.shouldSyncCalendar()).thenReturn(false); // Act listener.onPreferenceChanged(calendarPreferences, SettingsUtils.PREF_SYNC_CALENDAR); // Assert verify(mSessionUpdateLauncher).launchClearAllSessionsUpdate(); }
  • 41. @Test public void onPreferenceChangedClearedCalendar() throws Exception { // Arrange CUOSPCListener listener = new CUOSPCListener(mSessionUpdateLauncher); final CalendarPreferences calendarPreferences = mock(CalendarPreferences.class); when(calendarPreferences.shouldSyncCalendar()).thenReturn(false); // Act listener.onPreferenceChanged(calendarPreferences, SettingsUtils.PREF_SYNC_CALENDAR); // Assert verify(mSessionUpdateLauncher).launchClearAllSessionsUpdate(); }
  • 42. @Test public void onPreferenceChangedClearedCalendar() throws Exception { // Arrange CUOSPCListener listener = new CUOSPCListener(mSessionUpdateLauncher); final CalendarPreferences calendarPreferences = mock(CalendarPreferences.class); when(calendarPreferences.shouldSyncCalendar()).thenReturn(false); // Act listener.onPreferenceChanged(calendarPreferences, SettingsUtils.PREF_SYNC_CALENDAR); // Assert verify(mSessionUpdateLauncher).launchClearAllSessionsUpdate(); }
  • 43. class CalendarUpdatingOnSharedPreferenceChangedListener { void onPreferenceChanged(CalendarPreferences calendarPreferences, String key) { if (SettingsUtils.PREF_SYNC_CALENDAR.equals(key)) { if (calendarPreferences.shouldSyncCalendar()) { mSessUpdaterLauncher.launchAddAllSessionsUpdater(); } else { mSessUpdaterLauncher.launchClearAllSessionsUpdate(); } } } }
  • 44. Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
  • 45. Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
  • 47. –Michael Feathers “The fundamental thing to recognize is that when we look at a call in an object-oriented program, it does not define which method will actually be executed.”
  • 49. The code that needs dependencies is not responsible for getting them
  • 50. Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
  • 51. Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
  • 53. private void setupCards(CollectionView.Inventory inventory) { if (SettingsUtils.isAttendeeAtVenue(getContext())) { if (!hasAnsweredConfMessageCardsPrompt(getContext())) { inventoryGroup = new InventoryGroup(GROUP_ID_MESSAGE_CARDS); MessageData conferenceMessageOptIn = MessageCardHelper .getConferenceOptInMessageData(getContext()); inventoryGroup.addItemWithTag(conferenceMessageOptIn); inventoryGroup.setDisplayCols(1); inventory.addGroup(inventoryGroup); } // ... } }
  • 54. private void setupCards(CollectionView.Inventory inventory) { if (SettingsUtils.isAttendeeAtVenue(getContext())) { if (!hasAnsweredConfMessageCardsPrompt(getContext())) { inventoryGroup = new InventoryGroup(GROUP_ID_MESSAGE_CARDS); MessageData conferenceMessageOptIn = MessageCardHelper .getConferenceOptInMessageData(getContext()); inventoryGroup.addItemWithTag(conferenceMessageOptIn); inventoryGroup.setDisplayCols(1); inventory.addGroup(inventoryGroup); } // ... } }
  • 55. private void setupCards(CollectionView.Inventory inventory) { if (SettingsUtils.isAttendeeAtVenue(getContext())) { if (!hasAnsweredConfMessageCardsPrompt(getContext())) { inventoryGroup = new InventoryGroup(GROUP_ID_MESSAGE_CARDS); MessageData conferenceMessageOptIn = MessageCardHelper .getConferenceOptInMessageData(getContext()); inventoryGroup.addItemWithTag(conferenceMessageOptIn); inventoryGroup.setDisplayCols(1); inventory.addGroup(inventoryGroup); } // ... } }
  • 56. class Presenter { public void presentCards() { if (mIsAttendeeAtVenue) { if (!mMsgSettings.hasAnsweredMessagePrompt()) { mExploreView.addMessageOptInCard(); } // Stuff } } }
  • 57. class Presenter { public void presentCards() { if (mIsAttendeeAtVenue) { if (!mMsgSettings.hasAnsweredMessagePrompt()) { mExploreView.addMessageOptInCard(); } // Stuff } } }
  • 58. class Presenter { public void presentCards() { if (mIsAttendeeAtVenue) { if (!mMsgSettings.hasAnsweredMessagePrompt()) { mExploreView.addMessageOptInCard(); } // Stuff } } }
  • 59. class Presenter { public void presentCards() { if (mIsAttendeeAtVenue) { if (!mMsgSettings.hasAnsweredMessagePrompt()) { mExploreView.addMessageOptInCard(); } // Stuff } } }
  • 60. Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
  • 61. Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
  • 62. –Michael Feathers “[code] contains calls to code in other files. Linkers…resolve each of the calls so that you can have a complete program at runtime…you can usually exploit [this] to substitute pieces of your program”
  • 63. Use Link Seams for Espresso Tests
  • 66. public class PresenterFragmentImpl extends Fragment implements Presenter, UpdatableView.UserActionListener, LoaderManager.LoaderCallbacks<Cursor> { @Override public Loader<Cursor> onCreateLoader(int id, Bundle args) { Loader<Cursor> cursorLoader = createLoader(id, args); mLoaderIdlingResource.onLoaderStarted(cursorLoader); return cursorLoader; } @Override public void onLoadFinished(Loader<Cursor> loader, Cursor data) { processData(loader, data); mLoaderIdlingResource.onLoaderFinished(loader); } }
  • 67. public class PresenterFragmentImpl extends Fragment implements Presenter, UpdatableView.UserActionListener, LoaderManager.LoaderCallbacks<Cursor> { @Override public Loader<Cursor> onCreateLoader(int id, Bundle args) { Loader<Cursor> cursorLoader = createLoader(id, args); mLoaderIdlingResource.onLoaderStarted(cursorLoader); return cursorLoader; } @Override public void onLoadFinished(Loader<Cursor> loader, Cursor data) { processData(loader, data); mLoaderIdlingResource.onLoaderFinished(loader); } }
  • 68. public PresenterFragmentImpl addPresenterFragment(int uVResId, Model model, QueryEnum[] queries, UserActionEnum[] actions){ //... if (presenter == null) { //Create, set up and add the presenter. presenter = new PresenterFragmentImpl(); //... } else { //... } return presenter; }
  • 69. public PresenterFragmentImpl addPresenterFragment(int uVResId, Model model, QueryEnum[] queries, UserActionEnum[] actions){ //... if (presenter == null) { //Create, set up and add the presenter. presenter = new PresenterFragmentImpl(); //... } else { //... } return presenter; }
  • 72. flavorDimensions 'datasource', 'features' productFlavors { mock { dimension 'datasource' } prod { dimension 'datasource' } free { dimension 'features' } }
  • 73. Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
  • 74. Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
  • 77. Use Link Seams to swap out factories so you can use object seams
  • 78. Use Link Seams to swap out factories so you can use object seams
  • 79. public class FragFactory { public PresenterFragmentImpl make() { return new PresenterFragmentImpl(); } } public class FragFactory { public PresenterFragmentImpl make() { return new MockPresenterFragmentImpl(); } }
  • 80. public class FragFactory { public PresenterFragmentImpl make() { return new PresenterFragmentImpl(); } } public class FragFactory { public PresenterFragmentImpl make() { return new MockPresenterFragmentImpl(); } }
  • 81. public class FragFactory { public PresenterFragmentImpl make() { return new PresenterFragmentImpl(); } } public class FragFactory { public PresenterFragmentImpl make() { return new MockPresenterFragmentImpl(); } }
  • 82. public PresenterFragmentImpl addPresenterFragment(int uVResId, Model model, QueryEnum[] queries, UserActionEnum[] actions){ //... if (presenter == null) { //Create, set up and add the presenter. presenter = new PresenterFragmentImpl(); // 1 seam //... } else { //... } return presenter; }
  • 83. public PresenterFragmentImpl addPresenterFragment(int uVResId, Model model, QueryEnum[] queries, UserActionEnum[] actions){ //... if (presenter == null) { //Create, set up and add the presenter. presenter = mFragFactory.make(); // 2 seams //... } else { //... } return presenter; }
  • 84. This second seam buys you “mock mode”
  • 85. Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
  • 86. Tested apps are better apps, but building them is tough. They have seams. DI gives you Object Seams, which is why MVP helps testability. Build Variants give you Link Seams, but don’t overuse them.
  • 88. • “Microservices: Software That Fits in Your Head” • “Mark Zuckerberg: How to Build the Future” • Growing Object Oriented Software Guided by Tests • Working Effectively with Legacy Code • “Dependency Injection” by Martin Fowler • “Android Apps with Dagger” by Jake Wharton Sources