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

Android Unit Test Framework
http://pivotal.github.com/robolectric
Follow us on twitter: @robolectric
Wednesday, October 27, 2010

Tyler Schultz
Agile 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:

Why Unit Test?

Pivotal Labs
• www.pivotallabs.com
• San Francisco (Headquarters), NewYork,
Boulder, Singapore
• Primarily Rails - we do mobile too!
• Agile, XP, Continuos Integration, Pair
Programming

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.ThankYou 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 Robolectric
vs.Android Instrumentation Tests?
• Tests Run outside of the emulator in a JVM,
not the DalvikVM
- Running in a DalvikVM 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 Robolectric
vs.Android Instrumentation Tests?
• Iterate quickly!
• The latest Pivotal Android project is using
Robolectric boasting 1,047 tests that run in 28
seconds!

Why Use Robolectric
vs. 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 Robolectric
vs. 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?

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

RobolectricSample
Ant 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.

RobolectricSample
Project 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
@Test
public 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 Tests
Accessing the Shadow Object
<ImageView
android:id=”@+id/logo”
android:layout_width=”wrap_content”
android:layout_height=”wrap_content”
android:src=”@drawable/logo” />
...
@Test
public 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 Objects
Robolectric.bindAllShadowClasses()
• Where shadow objects are registered into
Robolectric
• This is a current listing of all the shadow objects
provided by Robolectric

Robolectric
Roadmap
• 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/robolectric
http://pivotal.github.com/RoblectricSample
twitter: @robolectric

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

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