TDD Android Applications with Robolectric

Android Unit Test Frameworkhttp://pivotal.github.com/robolectric Follow us on twitter: @robolectric

Joe Moore @joem Pivotal Labs @pivotallabshttp://svy.mk/robolectric

DisclaimerI’m mostly a Ruby guy now

AgendaTesting Approaches and AlternativesHow Robolectric worksWorkshop - TDD and SetupHow to extend Robolectric

Agile web consulting companyRuby on Rails, Android and iOSXP, TDD, Pair ProgrammingSF, NYC, Boulder, Singapore… and Atlanta!

We Test Stuff Cedar BDD for iOSJsUnit

On to the Android!

java.lang.RuntimeException(“Stub!”)

Google stripped the classes in android.jar and replaced their method bodies with:java.lang.RuntimeException(“Stub!”)

Every Test Failsjava.lang.RuntimeException: Stub! at android.content.Context.<init>(Context.java:4) at android.content.ContextWrapper.<init>(ContextWra atandroid.view.ContextThemeWrapper.<init>(ContextThemeWr5) at android.app.Activity.<init>(Activity.java:6) at com.pivotallabs.NamesActivity.<init>(NamesActivi

Additional Android testing challengesMany of the classes and methods are ﬁnalLack of interfacesNon public constructorsstatic methods

It’s Getting Better CalculonA testing DSL for Google Android

How have you been testing?

Android Testing

Android Testing• F@*#-it!

Android Testing• F@*#-it!• Integration-style: Android InstrumentationTests/Robotium

Android Testing• F@*#-it!• Integration-style: Android InstrumentationTests/Robotium• Library of tested POJO’s

Android Testing• F@*#-it!• Integration-style: Android InstrumentationTests/Robotium• Library of tested POJO’s• Mocking framework

Why use Robolectric?

vs. Android Instrumentation Tests? Instrumentation Tests are SLOW Instrumentation Tests require dexing, packaging and installation on an emulator or device to run in the Dalvik VM.

vs. Android Instrumentation Tests? Robolectric runs in the regular JVM: FAST No dexing, packaging, deploying, etc. The latest Pivotal Android project is using Robolectric:1,047 tests run in 28 seconds!

vs. POJO lib approach?Test ALL your code, not just non-Androidcode -- increased test coverage.… But well-tested code libraries are still agood idea.

vs. POJO lib approach?Robolectric is compatible with the waymost Android developers work:putting lots of stuff in Activities vs. havingcomplex object models.

vs. Mock approach?Mocking frameworks can lead to tests thatare reverse implementation of the codeCan lead to tests that are hard to readCan lead to tests that don’t help refactoring

Robolectric lets you:Iterate quicklyWrite black box style of testsTest behavior instead of implementationHave high test coverage

How does it work?Shadow ObjectsView and Resource Loading

How does it work? Shadow ObjectsMaybe they should have been called proxies.

How does it work? Shadow Objects1. Robolectric intercepts the loading of Android classes under test

How does it work? Shadow Objects1. Robolectric intercepts the loading of Android classes under test2. Rewrites the method bodies of Android classes (using javassist)

How does it work? Shadow Objects1. Robolectric intercepts the loading of Android classes under test2. Rewrites the method bodies of Android classes (using javassist)3. Binds “shadow objects” to new Android objects

How does it work? Shadow Objects1. Robolectric intercepts the loading of Android classes under test2. Rewrites the method bodies of Android classes (using javassist)3. Binds “shadow objects” to new Android objects4. The modified Android objects then proxy

How does it work? Shadow Objects Shadow Button getText()myButton.getText() Button (Android) return “Okay” return “Okay” text=“Okay”

How does it work? Shadow Objects ShadowmyButton.getSomething() Button getSomething() Button (Android) return null; Does not implement getSomething()

How does it work? Shadow Objects• Shadows are proxies for the Android classes• i.e. ShadowImageView “shadows” ImageView• AndroidObject.someMethod() => proxies to => ShadowAndroidObject.someMethod()• State is recorded so it can be verified in tests

How does it work? View and Resource Loading• Robolectric parses layout ﬁles and builds a view object tree made of Android view objects and their shadows.• Many view xml attributes are applied to the view object• Strings, string arrays, and color resources

How can I get started?• http://pivotal.github.com/robolectric/ index.html• http://github.com/pivotal/ RobolectricSample

Robolectric IDE• We are IntelliJ guys• Eclipse works, too• Maven!

Writing Tests

Writing TestsTests that reference Android need to be annotated: ... @RunWith(RobolectricTestRunner.class) public class MyActivityTest { @Test public void shouldDoWizbangFooBar() { ...

Writing Tests Often Robolectric is InvisibleButton pressMeButton = homeActivity.findViewById(R.id.press_me_button);assertThat((String) pressMeButton.getText(), equalTo("Tests Rock!"));

Writing Tests Often Robolectric is InvisibleButton pressMeButton = homeActivity.findViewById(R.id.press_me_button);assertThat((String) pressMeButton.getText(), equalTo("Tests Rock!")); No sign of Robolectric, Shadows, etc.

Writing Tests Talking to ShadowsShadowActivity shadowActivity = shadowOf(homeActivity);Intent startedIntent = shadowActivity.getNextStartedActivity();ShadowIntent shadowIntent = shadowOf(startedIntent);

Writing Tests Talking to ShadowsShadowActivity shadowActivity = shadowOf(homeActivity);Intent startedIntent = shadowActivity.getNextStartedActivity();ShadowIntent shadowIntent = shadowOf(startedIntent); Many test-only methods are added to Shadow classes

Writing Tests Talking to ShadowsShadowActivity shadowActivity = shadowOf(homeActivity);Intent startedIntent = shadowActivity.getNextStartedActivity();ShadowIntent shadowIntent = shadowOf(startedIntent); Many test-only methods are added to Shadow classes Example: capturing object state

Writing Tests Talking to Shadows<ImageView android:id=”@+id/logo” android:layout_width=”wrap_content” android:layout_height=”wrap_content” android:src=”@drawable/logo” />...@Testpublic void logoImageViewShouldUseTheLogoDrawable() { ImageView logo = (ImageView) activity.findViewById(R.id.logo); // imageView only provides logo.getDrawable(); ShadowImageView logoShadow = Robolectric.shadowOf(logo); assertThat(logoShadow.resourceId, equalTo(R.drawable.logo));}

Extending Robolectric Help Robolectric cover more of Android

Writing Shadow• @RealObject• __constructor__• @Implements• @Implementation• Robolectric.bindAllShadowClasses()

Shadow Objects @RealObject• Robolectric is using reflection to instantiate the shadow object (default or no-args constructor)• Robolectric will inject the Android object onto shadow object’s fields annotated with @RealObject

Shadow Objects @RealObject@Implements(View.class)public class ShadowView { @RealObject private View realView; private int id;...

Shadow ObjectsShadow inheritance works.If no shadow class is registered for anAndroid class, the Android object’s superconstructor will seek out a shadow class,up through the constructor super chain untilone is found.

Shadow Objects__constructor__Implementations of Android constructors.When Robolectric is finished instantiatingthe shadow object, it will attempt to invokea method on the shadow named__constructor__ that has the sameargs as the Android object’s constructor

Shadow Objectspublic class Intent { public Intent(String action, Uri uri) { /* compiled code */ } ...}public class ShadowIntent { public void __constructor__(String action,Uri uri) { ... } ...}

Shadow Objects@Implements(View.class)public class ShadowView { @RealObject private View realView; private int id;...

Shadow Objectspublic class ShadowTextView {... @Implementation public CharSequence getText() { return text; }...

Shadow ObjectsRobolectric.bindAllShadowClasses() • Where shadow objects are registered into Robolectric • This is a current listing of all the shadow objects provided by Robolectric

Thanks! Joe Moore @joem Pivotal Labs @pivotallabshttp://svy.mk/robolectric

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TDD Android Applications with Robolectric

by Joseph Moore

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