Automated Testing for Modern Android Applications 

Andy Dyer +AndrewDyer @dammitandy 

No content

Making Android apps testable 

Dynamic languages Tests shouldn't drive implementation. 

Static languages You know nothing. 

Making Android apps testable 1. Dependency injection 2. Mocking & stubbing 3. Unit & integration tests 

Dependency injection 

Dependency injection • Classes receive dependencies, don’t have to know where to find them or how to create them • Swap components for mocks in tests • Use different components for different build flavors, etc. 

Basic dependency injection public class Beer implements Reinheitsgebot { Water water; Barley barley; Hops hops; public Beer(Water water, Barley barley, Hops hops) { this.water = water; this.barley = barley; this.hops = hops; } } 

Dagger A Java dependency injection library 

Dagger • Defining dependencies at compile time avoids reflection at runtime • Compiler validates components, modules, and injections • Dagger 2 is currently in alpha, but already being used by Google in production apps google.github.io/dagger/ 

Dagger Modules @Module public class MyModule { @Provides @Singleton public MyService provideMyService() { return new MyService(); } } 

Dagger Components @Component(modules = MyModule.class) public interface Graph { void inject(Activity activity); void inject(Fragment fragment); public final static class Initializer { public static Graph init(boolean mockMode) { return Dagger_Graph.builder().build(); } } } 

Dagger Object Graph public class MyApplication extends Application { @Getter static DemoApplication instance; @Getter Graph graph; @Override public void onCreate() { super.onCreate(); instance = this; graph = Graph.Initializer.init(false); } public void setMockMode(boolean useMock) { graph = Graph.Initializer.init(useMock); } } 

Dagger dependency injection public class MyFragment extends Fragment { @Inject MyService service; @Override public void onViewCreated(View view, Bundle savedInstanceState) { MyApplication.getInstance().getGraph().inject(this); service.getMyData(); } } 

Learning more about Dagger • Jake Wharton - Dependency Injection with Dagger 2 parleys.com/play/5471cdd1e4b065ebcfa1d557 • Gregory Kick - Dagger 2: A New Type of Dependency Injection youtube.com/watch?v=oK_XtfXPkqw 

Mocking & Stubbing 

Mocking & Stubbing • Substitute runtime implementation for something that can be predictably tested in isolation • Verify behavior 

A Java mocking library 

Mockito • Mock/stub dependencies and function return values • Inject mocks to validate behavior in tests • Use included Hamcrest matchers for clear, readable tests code.google.com/p/mockito/ 

Using Mockito // create mock MyClass mocked = mock(MyClass.class); // specify behavior when(mocked.doSomething()).thenReturn(somethingElse); // verify method calls verify(mocked).getMyData(anyInt(), anyString()); 

Using Mockito // capture arguments ArgumentCaptor captor = ArgumentCaptor.forClass(Callback.class); verify(authenticationService).login(anyString(), anyString(), captor.capture()); // simulate error conditions, etc. captor.getValue().failure(RetrofitError.unexpectedError( "Invalid password", new Exception())); 

Unit & Integration Tests 

Tests or it didn't happen 

Unit testing public class BeerTest extends InstrumentationTestCase { @Inject Beer beer; @Override protected void setUp() throws Exception { MyApplication.getInstance().getGraph().inject(this); } public void testBeerIsGood() { assertTrue(beer.isGood()); } } 

An Android UI testing library 

Espresso • Handles activity creation & state sync • Simple, concise API • Really fast! code.google.com/p/android-test-kit* 

UI testing with Espresso public class MyActivityTest extends ActivityInstrumentationTestCase2 { public MyActivityTest() { super(MyActivity.class); } @Override protected void setUp() throws Exception { super.setUp(); getActivity(); // trigger activity launch } public void testInvalidEmailShowsError() { onView(withId(R.id.email)).perform(typeText("abc"), closeSoftKeyboard()); onView(withId(R.id.email_sign_in_button)).perform(click()); onView(withId(R.id.email)).check(matches(withError( getActivity().getString(R.string.error_invalid_email)))); } } 

Sample application • Dagger object graph • Retrofit API with sample request • Lombok & Android Studio plugin • Login activity • Activity with fragment to make API request and display data 

Testing the login activity • Simulate data entry and taps to validate UI functionality • Simulate an error without making a network request 

Testing the main activity • Verify the RecyclerView contains data • Simulate taps to validate the appropriate URLs are loaded in a WebView 

Testing the API • Use mock API response loaded from text file to validate JSON parsing 

Demo 

Known issues • Some tests may fail on older devices/emulators such as those running < API 18. Hopefully this will be fixed soon by an update to the test support library. 

Additional resources • Bryan Stern/Circle Engineering - Instrumentation Testing with Dagger, Mockito, and Espresso engineering.circle.com/instrumentation-testing-with-dagger- mockito-and-espresso 

Conclusion Using dependency injection, mocking, and automated testing tools helps us build better apps. Working together as a community, we can make testing even easier. 

Questions? 

Slides speakerdeck.com/abdyer/mce2015-automated-testing-for- modern-android-applications Code github.com/abdyer/android-test-demo/releases/tag/ mceconf-2015 +AndrewDyer @dammitandy