1. How to build rock-solid apps and
keep 100m+ users happy
Iordanis Giannakakis

2. About me
• Iordanis “Jordan” Giannakakis
• Android Team Lead at Shazam
• @iordanis_g
@iordanis_g

3. How Shazam works
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4. 100+ million users
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5. Happy users
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Even developers?

6. Android testing
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7. Faster release cycles
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8. Better code
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9. Cheaper
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http://testdroid.com/testdroid/5851

10. Easy
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11. A user walks into a bar...
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12. Doing it the test-driven way
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Write
UI test
Implement
Refactor
Write unit
test
BDD
TDD

13. “To TDD or not to TDD?
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...That is not the question”
Seb Rose
http://claysnow.co.uk/to-tdd-or-not-to-tdd/

14. Test-first
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• Generally easier
• Eliminates external dependencies
• Easily repeatable

15. The Acceptance tests cycle
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Write
UI test
Implement
Refactor
Write unit
test
BDD
TDD

16. Acceptance criteria
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Given: arrange
When: act
Then: assert

17. Example
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Given a user is near a music venue
And the server always returns a known result
When the user Shazams
Then the user can check-in their discovery

18. gwen
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given(user).isNear(lexington())
given(server).returns(lustForLife())
when(user).shazams()
then(user).canCheckIn(lustForLife(), lexington())
https://github.com/shazam/gwen

19. Acceptance tests technologies
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• Instrumentation
• JUnit 3
• Robotium & Espresso
• gwen
• HamMock Server

20. The Unit tests cycle
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Write
UI test
Implement
Refactor
Write unit
test
BDD
TDD

21. What we don’t test
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Activities & Fragments
https://github.com/xxv/android-lifecycle/

22. What we don’t test
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23. What we do unit test
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• Presentation logic
• Business logic
• That’s all!

24. The MVP pattern
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Presenter
Model View

25. The MVP pattern, for Android
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Presenter
Model
View
start
stop
Android

26. The MVP pattern
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• Makes presentation logic testable
• No need to test the “slave” view
• Avoid Android dependencies

27. Dependency Injection, Yourself (DIY)
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• Break hardcoded dependencies
• Behaviour vs implementation
• Swappable dependencies for test and
production runtimes

28. Hard-coded dependencies
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Client
Feature X Feature X

29. Dependency Injection
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Client
Injector
Feature X
Interface

30. Model
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public interface VenueRetriever {
void findClosestVenue(VenueFoundCallback callback);
}
public class NetworkVenueRetriever implements VenueRetriever {
public void findClosestVenue(VenueFoundCallback callback) {
// Some slow networking
}
}
public class LocalVenueRetriever implements VenueRetriever {
public void findClosestVenue(VenueFoundCallback callback) {
// DB look-up / caching layer, perhaps?
}
}

31. Activity
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public class ResultActivity extends Activity implements ResultView {
private final VenueRetriever venueRetriever;
private ResultPresenter resultPresenter;
public ResultActivity() {
venueRetriever = venueRetriever();
}
public void onCreate(Bundle savedInstanceState) {
// TODO: Setup layouts & views
Result result = resultToDisplay();
resultPresenter = new ResultPresenter(this, venueRetriever, result);
}
public void onStart() {
resultPresenter.startPresenting();
}
}

32. Presenter
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public class ResultPresenter {
public ResultPresenter(ResultView resultView, VenueRetriever
venueRetriever, Result result) {
this.resultView = resultView;
this.venueRetriever = venueRetriever;
this.result = result;
}
public void startPresenting() {
resultView.showResult(result);
venueRetriever.findClosestVenue(new VenueFoundCallback() {
public void venueFound(Venue venue) {
resultView.showCheckInPrompt(venue);
}
});
}
}

33. View
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public interface ResultView {
void showResult(Result track);
void showCheckInPrompt(Venue venue);
}

34. Activity
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public class ResultActivity extends Activity implements ResultView {
public void showResult(Result result) {
//TODO show the result screen & bind result data
}
public void showCheckInPrompt(Venue venue) {
//TODO bind the venue with check-in prompt view
}
}

35. Unit tests technologies
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• JUnit 4
• Robolectric
java.lang.RuntimeException: Stub!
• Hamcrest
• JMock

36. Test execution
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37. Continuous Integration
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38. Speed (Hint: slow)
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39. Usual execution
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Test Suite

40. Spoon
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http://square.github.io/spoon/

41. Fork
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Test Suite

42. Fork
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• Inspired by Spoon, but faster
• Infinitely scalable
• Current setup 1 test / 2 secs
• Pooled execution

43. Flakiness monitor
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44. ADB Remote
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https://github.com/sleekweasel/CgiAdbRemote

45. If all else fails...
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46. If all else fails...
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47. If all else fails...
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48. Summary
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• Testing is easier than you may think
• Practice, practice, practice
• Toolset is limited
• Ship it!

49. @iordanis_g
Questions?
Hiring...