We’ll introduce MockWebServer, AssertJ for android and some Robolectric tips and tricks that will help you setup and write unit tests in no time.

1. Testing with
Robolectric
IVAN KUŠT, ANDROID TEAM LEADER

2. ROBOLECTRIC
• http://robolectric.org/
• unit test framework
• tests run in JVM on your machine

3. CODE EXAMPLE
• https://github.com/infinum/Dagger-2-Example

4. 01SETTING UP ROBOLECTRIC

5. ROBOLECTRIC SETUP
1. Add gradle dependencies
2. write test Application class
3. write test class
4. run tests

6. 1. ADD DEPENDENCIES
• make sure “Unit tests” is selected as Test Artifact under
Build Variants
• add the robolectric dependency in your app build.gradle file:
// Robolectric
testCompile 'junit:junit:4.12'
testCompile 'org.hamcrest:hamcrest-library:1.3'
testCompile 'org.apache.maven:maven-ant-tasks:2.1.3' // fixes issue on linux/mac
testCompile('org.robolectric:robolectric:3.0')

7. 2. WRITE TEST APPLICATION CLASS
• all unit test code goes into test flavour
• Test{applicationName}
• must extend your application class
• runs instead of application class in tests
• should inject test dependencies

8. 3. WRITE TEST CLASS
• create new class in test flavor
• specify runner with @RunWith annotation
• add @Config annotation
• add test methods and annotate them with @Test

9. 3.5 TEST CONFIGURATION
• constants property of @Config annotation is mandatory
• options (except constants) can be specified in a file instead:
/test/resources/robolectric.properties
• for other options check:
http://robolectric.org/configuring/
@RunWith(RobolectricGradleTestRunner.class)
@Config(constants = BuildConfig.class, sdk = 21)
public class DeckardActivityTest {
@Test
public void testSomething() throws Exception {
assertTrue(Robolectric.setupActivity(DeckardActivity.class) != null);
}
}

10. 4. RUN TESTS
• from Android studio
• ./gradlew clean test

11. TEST REPORT
• will be generated in:
/app/build/reports/tests/{flavour}/index.html
• if tests faill, gradle will print out the location of the report in
console as well

12. LOGS
• to show Log.d() outputs add following in your @Before
method:
ShadowLog.stream = System.out;

13. 01SYNCHRONOUS EXECUTORS

14. (A)SYNCHRONOUS EXECUTORS
• unit tests run in a single thread
• waiting for background threads complicates tests
• solution: Synchronous executors (for Retrofit)

15. SETUP
• setting executor on Retrofit:
• specify executor for networking and callbacks
• for tests: both synchronous
return new RestAdapter.Builder()
...
.setExecutors(new BackgroundExecutor(), new CallbackExecutor())
...
.build();

16. SYNCHRONOUS EXECUTOR?
• runs the queued runnable in the same thread
• simple as that:
public class SynchronousExecutor implements Executor {
@Override
public void execute(Runnable command) {
command.run();
}
}

17. 01MOCK WEB SERVER

18. MOCK WEB SEVER
• part of OkHttp library by Square
• network responses must be mocked in unit tests
• speed
• consistency

19. MOCK WEB SERVER DEPENDENCIES
• add the MockWebServer dependency in your app
build.gradle file:
• MockWebServer depends on OkHttp library
• make sure that versions match
testCompile ‘com.squareup.okhttp:mockwebserver:2.4.0'

20. USING MOCKWEBSERVER
1. Instantiate MockWebServer
2. call start() method
3. get local server url by calling url(“/“)
4. inject local server url into networking module
5. enqueue responses using enqueue() method

21. INSTANTIATING MOCK WEB SERVER
• prepare and inject MockWebServer in @Before method
(called before every @Test method)
• stop MockWebServer in @After method (called after every
@Test method)

22. INSTANTIATING MOCK WEB SERVER
• another option:
• implement TestLifecycleApplication in Test application
class
• prepare and inject MockWebServer in
beforeTest(Method) method in Test application class
• stop MockWebServer in:
afterTest(Method) in Test application class

23. ENQUEUEING RESPONSES
• enqueue(), MockResponse object
• https://github.com/square/okhttp/blob/master/
mockwebserver/src/main/java/com/squareup/okhttp/
mockwebserver/MockResponse.java
mockWebServer.enqueue(
new MockResponse()
.setResponseCode(200)
.setBody(“Response body”)
);

24. WHAT ABOUT LARGE RESPONSES?
1. Store response body content to a file
2. put the file inside /test/resources/ directory
3. read the contents of the file in test:
public static String readFromFile(String filename) {
InputStream is = ResourceUtils.class.getClassLoader().getResourceAsStream(filename));
return convertStreamToString(is);
}

25. CHECKING REQUESTS
• mockWebServer.getRequestCount()
• mockWebServer.takeRequest()
• mockWebServer.takeRequest(long, TimeUnit)

26. EXAMPLE
@Test
public void nameOk() throws Exception {
PokemonTestApp.getMockWebServer().enqueue(
new MockResponse()
.setResponseCode(200)
.setBody(ResourceUtils.readFromFile("charizard.json"))
);
String resourceUri = "api/v1/pokemon/6/";
Pokemon pokemon = new Pokemon();
pokemon.setResourceUri(resourceUri);
Activity activity = buildActivity(pokemon);
RecordedRequest request = takeLastRequest();
//Perform the assertions
}

27. 01SHADOW CLASSES

28. SHADOW CLASSES
• if your project structure prevents you from injecting mock
classes in unit tests
• any class can be swapped with a “shadow” class

29. SHADOWING A CLASS
1. Create a custom Robolectric runner
2. Declare shadowed classes in createClassLoaderConfig()
method
3. Implement shadow class
4. Add shadow classes to tests in @Config
5. Run tests with custom runner

30. CREATE A CUSTOM RUNNER
public class CustomRobolectricTestRunner extends RobolectricTestRunner {
/**
* Creates a runner to run {@code testClass}. Looks in your working directory for your
* AndroidManifest.xml file
* and res directory by default. Use the {@link Config} annotation to configure.
*
* @param testClass the test class to be run
* @throws InitializationError if junit says so
*/
public CustomRobolectricTestRunner(Class<?> testClass) throws InitializationError {
super(testClass);
}
/**
* Declare custom classes to be shadowed when shadow exist.
*/
public InstrumentationConfiguration createClassLoaderConfig() {
InstrumentationConfiguration.Builder builder =
InstrumentationConfiguration.newBuilder();
builder.addInstrumentedClass(GoogleCloudMessaging.class.getName());
return builder.build();
}
}

31. IMPLEMENT SHADOW CLASS
• create a new class with @Implements(OriginalClass.class)
annotation
• add @Implementation annotation to methods that “override”
behaviour from original class
• you can leave some methods unchanged
• if you wish to use an instance of OriginalClass in your
shadow class it must be annotated with @RealObject and
accessed through reflection

32. ADD SHADOWS TO TEST
• in order to make your shadows available in test add them to
@Config in your test:
@Config(shadows = {ShadowClass.class})

33. EXAMPLE SHADOW CLASS
@Implements(GoogleCloudMessaging.class)
public class ShadowGoogleCloudMessageing {
@Implementation
public void close() {
Log.d("GoogleCloudMessageing", "close()");
}
@Implementation
public void send(String to, String msgId, Bundle data) throws IOException {
Log.d("GoogleCloudMessageing", "send()");
}
@Deprecated
@Implementation
public synchronized String register(String... senderIds) throws IOException {
Log.d("GoogleCloudMessageing", "register()");
return "1234567890";
}
@Implementation
public String getMessageType(Intent intent) {
Log.d("GoogleCloudMessageing", "getMessageType()");
return "gcm";
}
}

34. 01ASSERT J ANDROID

35. ASSERT J ANDROID
• https://github.com/square/assertj-android
• extension of AssertJ
• you can extend and set up your own assertions

36. EXAMPLE
//Check that name in details is displayed properly.
assertThat(activity.findViewById(R.id.name).getVisibility())
.isEqualTo(View.VISIBLE);
assertThat(((TextView) activity.findViewById(R.id.name))
.getText()).isEqualTo("Charizard");

37. SUMMARY
• use Robolectric for tests of a single Activity or Fragment
• use synchronous executors with Retrofit in tests
• use MockWebServer to easily mock out network responses
• use Shadows for classes that you can’t replace via
dependency injection
• AssertJ Android simplifies your assertions on Android stuff

38. CODE EXAMPLE
• https://github.com/infinum/Dagger-2-Example

39. Thank you!
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