Learn How to Unit Test Your Android Application (with Robolectric)

Android Unit Test Framework

http://pivotal.github.com/robolectricFollow us on twitter: @robolectric

Wednesday, October 27, 2010

http://pivotal.github.com/robolectric


Tyler SchultzAgile Engineer, Pivotal Labs


Talking Points

• Testing Approaches and Alternatives

• How Robolectric works

• How to extend Robolectric

• Workshop - write tests & help getting you setup


Pivotal Labs

• Jasmine - Javascript BDD test framework, @jasminebdd

• Cedar - iOS/Objective-C BDD test framework, @cedarbdd

• Pivotal Tracker - www.pivotaltracker.com

You may have heard of us:


http://www.pivotaltracker.com

http://www.pivotaltracker.com

Why Unit Test?


Pivotal Labs

• www.pivotallabs.com

• San Francisco (Headquarters), New York, Boulder, Singapore

• Primarily Rails - we do mobile too!

• Agile, XP, Continuos Integration, Pair Programming


http://www.pivotallabs.com

http://www.pivotallabs.com

java.lang.RuntimeException(“Stub!”)


Google has stripped the classes in the android.jar file and have had all their method bodies replaced with:

throw new RuntimeException(“Stub!”);


Additional Android testing challenges

• Many of the classes and methods are final

• Lack of interfaces

• Non public constructors

• static methods


sfandroid.org members, what have you been doing?


Android Testing Approaches


Android Testing Approaches

• No Tests! EGAD!

• Android InstrumentationTests/Robotium - integration style testing of Android apps

• Library of tested POJO’s, referenced from a non tested Android project

• Mocking framework such as Easy Mock and Mockito


Robolectric


Robolectric

• Christian Williams wrote the core while working on projects at Xtreme Labs of Toronto. Thank You Xtreme Labs!

• Robolectric is published under the MIT license


Robolectric

• Pivotal Labs has forked Xtreme Labs repo, renamed it to Robolectric, and expanded its functionality

• We’ve used Robolectric on several projects with great success!


Robolectric

Why use Robolectric?What makes it so great?


Why Use Robolectricvs. Android Instrumentation Tests?

• Tests Run outside of the emulator in a JVM, not the Dalvik VM

- Running in a Dalvik VM requires dexing, packaging and installation on an emulator or device - slow!

- Tests execute quickly in the JVM and execute slowly on the emulator


Why Use Robolectricvs. Android Instrumentation Tests?

• Iterate quickly!

• The latest Pivotal Android project is using Robolectric boasting 1,047 tests that run in 28 seconds!


Why Use Robolectricvs. POJO lib approach?

• The POJO lib approach leads to code proliferation, interfaces with multiple implementations - code bloat!

• Robolectric allows for vastly increased test coverage. Test ALL your code, not just non-Android code.


• Mocking frameworks can lead to tests that are reverse implementation of the code

• Can lead to tests that are hard to read

• Can lead to tests that don’t help refactoring

Why use Robolectricvs. Mock approach?


Why Use Robolectric?

• Iterate quickly

• Robolectric allows for a black box style of testing

• Test behavior instead of implementation

• High test coverage


How does it work?

Google has stripped the classes in the android.jar file and have had all their method bodies replaced with:

throw new RuntimeException(“Stub!”);


How does it work?

• Shadow Objects

• View and Resource Loading


How does it work?

• Robolectric intercepts the loading of Android classes under test

• Rewrites the method bodies of Android classes (using javassist)

• Binds new shadow objects to new Android objects

• The modified Android objects proxy method calls to the shadow objects

Shadow objects


How does it work?

• Shadows back the Android classes. i.e. ShadowImageView backs the ImageView class.

• Method calls to the Android object are proxied to the shadow object’s method of the same signature, if it exists.

• Simple implementations giving rudimentary behavior

• State is recorded so it can be verified in tests

Shadow objects


How does it work?

• Robolectric parses layout files and builds a view object tree made of Android view objects and, of course, their shadows.

• Some of the view xml attributes are applied to the view object (currently applies: id, visibility, enabled, text, checked, and src)

• Strings, string arrays, and color resources are parsed loaded too.

View and Resource Loading


• RobolectricSample is a project that is setup to use Robolectric

• http://github.com/pivotal/RobolectricSample

How can I get started?


http://github.com/pivotal/RobolectricSample

http://github.com/pivotal/RobolectricSample

Getting Started with Robolectric

$ git clone git://github.com/pivotal/RobolectricSample.git

$ cd RobolectricSample

$ git submodule update --init

$ android update project -p .

$ ant clean test

These commands are available on the RobolectricSample README file


RobolectricSampleAnt Support

• RobolectricSample provides a build.xml file which defines a test task

• Useful for Continuous Integration


Robolectric IDE support

• RobolectricSample is setup with IntelliJ project files. We’re using the latest IntelliJ EAP.

• Eclipse compatibility is currently unknown. We need help from the community getting Eclipse support!

• If nothing else, you should be able to use your favorite tooling to write your code and use the ant tasks to build and test.


RobolectricSampleProject Layout

• RobolectricSample - main Android module

• robolectric - module containing the robolectric test framework (also a git submodule)

• aidl - module containing any aidl files your project defines

• code - module where application code and tests go


Robolectric

Writing Tests


Writing Tests

...@RunWith(RobolectricTestRunner.class)public class MyActivityTest {

@Test! public void shouldDoWizbangFooBar() {...

Tests that reference Android need to be annotated:


Writing Tests@Testpublic void shouldShowLogoWhenButtonIsPressed() {

Activity activity = new MyActivity();activity.onCreate(null);ImageView logo = (ImageView) activity.findViewById(R.id.logo);Button button = (Button) activity.findViewById(R.id.button);

assertThat(logo.getVisibility(), equalTo(View.GONE));

button.performClick();

assertThat(logo.getVisibility(), equalTo(View.VISIBLE));}


Writing Tests

Dealing with cases where Android classes do not provide a way to retrieve object state


Writing TestsAccessing the Shadow Object

<ImageViewandroid: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));

}


Shadow Objects

• @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 Objects

• If no shadow class is registered for an Android class, the Android object’s super constructor will seek out a shadow class, up through the constructor super chain until one is found.


Shadow Objects__constructor__

• When Robolectric is finished instantiating the shadow object, it will attempt to invoke a method on the shadow named __constructor__ that has the same args as the Android object’s constructor


Shadow Objects__constructor__

public class Intent { public Intent(String action, Uri uri) { /* compiled code */ } ...}

public class ShadowIntent { public void __constructor__(String action, Uri uri) { ... } ...}


Shadow Objects@Implements

@Implements(View.class)public class ShadowView {

@RealObject private View realView; private int id;...


Shadow Objects@Implementation

public 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


RobolectricRoadmap

• Eclipse support

• Simplified setup - robolectric.jar

• continued shadow updates and additions

• resource overrides, i.e. hdpi, landscape, i18n, etc.


Q & A & Workshop!

• git clone git://github.com/pivotal/RobolectricSample.git

• Mac users can download the latest IntelliJ EAP from my machine: http://tschultz.local

• Add a button to the homepage of RobolectricSample that toggles the visibility of the robolectric logo. Tests First!

http://pivotal.github.com/robolectrichttp://pivotal.github.com/RoblectricSample

twitter: @robolectric


http://tschultz.local

http://tschultz.local



http://pivotal.github.com/RoblectricSample




Learn How to Unit Test Your Android Application (with Robolectric)

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