There are many tools, libraries and frameworks available for Android developers to test their applications. The jungle is huge and it's not easy to find the right ones. Some frameworks are good for unit testing, some are good for instrumentation testing, and some can be used for both. Some have great capabilities but annoying weaknesses. Some are good for testing UI, other allow you to make good mocks. We will look at many frameworks, the popular ones like Mockito, Robolectric, Espresso, and some other. Presented at GDG DevFest Pilsen 2016.

2. Unit Testing Experience on Android

4. Android apps are difficult to test

5. Types of Android tests

6. Types of Android tests
Instrumentation
tests
Local unit
tests

7. Android test code
• project sources
• ${module}/src/main/java
• instrumentation tests
• ${module}/src/androidTest/java
• unit tests
• ${module}/src/test/java
• full Gradle and Android Studio support

9. • the essential piece of both instrumentation and unit tests
• alone can be used only for pure Java
• doesn’t provide any mocks or Android APIs

10. Instrumentation Tests

11. Instrumentation Tests
• running on physical device or emulator
• gradle connectedAndroidTest
• ${module}/build/reports/androidTests/connected/
index.html

13. Instrumentation Tests
Legacy instrumentation tests
or
Testing Support Library

14. Legacy Instrumentation Tests
• JUnit3
• Tests extend from TestCase
• AndroidTestCase
• ActivityInstrumentationTestCase2
• ServiceTestCase
• …
deprecated
since API
level 24

15. Testing Support Library
• JUnit4 compatible
• AndroidJUnitRunner
android {
defaultConfig {
testInstrumentationRunner
"android.support.test.runner.AndroidJUnitRunner"
}
}
dependencies {
androidTestCompile 'com.android.support.test:runner:0.5'
}

16. Testing Support Library
• JUnit test rules
• AndroidTestRule
• ServiceTestRule
• DisableOnAndroidDebug
• LogLogcatRule
• …
androidTestCompile 'com.android.support.test:rules:0.5'

18. • framework for functional UI tests
• part of Android Testing Support Library
androidTestCompile
'com.android.support.test.espresso:espresso-core:2.2.2'

19. @Test
public void sayHello() {
onView(withId(R.id.edit_text))
.perform(typeText(STRING_TO_BE_TYPED), closeSoftKeyboard());
onView(withText("Say hello!"))
.perform(click());
String expectedText = "Hello, " + STRING_TO_BE_TYPED + "!";
onView(withId(R.id.textView))
.check(matches(withText(expectedText)));
}

20. Problems
• testing on device is not isolated
• device state affects the result
• e.g. screen on/off might affect test result
onView(withId(R.id.my_view))
.check(matches(isDisplayed()));

21. Some annoyances
android.support.test.espresso.NoActivityResumedException:
No activities in stage RESUMED.
Did you forget to launch the activity. (test.getActivity() or similar)?

22. Instrumentation tests
are
kinda
SLOOOOOW

23. Unit Tests

24. Unit Tests
• run on JVM
• mockable android.jar
• gradle test
• ${module}/build/reports/tests/${variant}/index.html

25. ...

27. • Helps rarely
• returns 0, false, null, …
Method ... not mocked.
android {
testOptions {
unitTests.returnDefaultValues = true
}
}

29. • mocking framework
• easy to use
• compatible with Android unit testing
testCompile 'org.mockito:mockito-core:2.2.11'

30. • can be used also in instrumentation tests
• needs dexmaker
androidTestCompile 'org.mockito:mockito-core:2.2.11'
androidTestCompile 'com.google.dexmaker:dexmaker:1.2'
androidTestCompile 'com.google.dexmaker:dexmaker-mockito:1.2'

31. @RunWith(JUnit4.class)
public class ContextManagerTest {
@Mock Context mAppContext;
@Before
public void setUp() {
MockitoAnnotations.initMocks(this);
}
@Test
public void testWithContext() {
…
}
}

32. @RunWith(MockitoJUnitRunner.class)
public class ContextManagerTest {
@Mock Context mAppContext;
@Test
public void testWithContext() {
…
}
}

33. @RunWith(JUnit4.class)
public class ContextManagerTest {
@Test
public void testWithContext() {
Context appContext = mock(Context.class);
Mockito.when(appContext.getPackageName())
.thenReturn(“com.example.app”);
…
}
}

34. • Mockito.spy()
• wrapping a real object
• Mockito.verify()
• verify that special condition are met
• e.g. method called, method called twice, …

35. Limitations
• final classes
• opt-in incubating support in Mockito 2
• anonymous classes
• primitive types
• static methods

37. • functional testing framework
• runs on JVM
• at first, might be difficult to use
• the ultimate mock of Android APIs
• provides mocks of system managers
• allows custom shadows

38. • possible to use for UI testing
• better to use for business logic
@RunWith(RobolectricTestRunner.class)
public class MyTest {
…
}

39. • Robolectric
• RuntimeEnvironment
• Shadows
• ShadowApplication
• ShadowLooper

40. Potential problems
• difficult to search for solutions
• long history of bigger API changes
• many obsolete posts

42. • Can mock static methods
• Can be used together with Mockito

43. @RunWith(PowerMockRunner.class)
@PrepareForTest(Static.class);
PowerMockito.mockStatic(Static.class);
Mockito.when(Static.staticMethod())
.thenReturn(value);
PowerMockito.verifyStatic(Static.class);

45. • “matchers on steroids”
• offers more complex checks
assertThat(myClass, isInstanceOf(MainActivity.class));
assertThat(myManager.getValue(), isEqualTo(someValue));
assertThat(value, isIn(listOfValues));
assertThat(value, not(isIn(listOfValues)));

47. • cross-platform BDD framework
• human-like test definitions
testCompile ‘junit:junit:4.12'
testCompile ‘info.cukes:cucumber-java:1.2.5'
testCompile 'info.cukes:cucumber-junit:1.2.5'

48. • describe the desired behaviour
Feature: CoffeeMaker
Scenario: a few coffees
Given I previously had 3 coffees
When I add one coffee
Then I had 4 coffees

49. • create the
mapping
public class CoffeeMakerDefs {
CoffeeMaker mCoffeeMaker = new CoffeeMaker();
}

50. • create the
mapping
public class CoffeeMakerDefs {
CoffeeMaker mCoffeeMaker = new CoffeeMaker();
@Given("^I previously had (d+) coffees$")
public void hadCoffeesPreviously(int coffees) {
mCoffeeMaker.setCoffeeCount(coffees);
}
}

51. • create the
mapping
public class CoffeeMakerDefs {
CoffeeMaker mCoffeeMaker = new CoffeeMaker();
@Given("^I previously had (d+) coffees$")
public void hadCoffeesPreviously(int coffees) {
mCoffeeMaker.setCoffeeCount(coffees);
}
@When("^I add one coffee$")
public void addCoffee() {
mCoffeeMaker.addCoffee();
}
}

52. • create the
mapping
public class CoffeeMakerDefs {
CoffeeMaker mCoffeeMaker = new CoffeeMaker();
@Given("^I previously had (d+) coffees$")
public void hadCoffeesPreviously(int coffees) {
mCoffeeMaker.setCoffeeCount(coffees);
}
@When("^I add one coffee$")
public void addCoffee() {
mCoffeeMaker.addCoffee();
}
@Then("^I had (d+) coffees$")
public void hadCoffees(int coffees) {
Assert.assertEquals(coffees, mCoffeeMaker.getCoffeeCount());
}
}

53. • place definition and mapping at the same paths!
• ${module}/src/test/java/com/example/MyMapping.java
• ${module}/src/test/resources/com/example/
MyDefinition.feature
@RunWith(Cucumber.class)
public class RunCucumberTest {
}

54. Code Coverage

55. Code Coverage
• instrumentation tests
• JaCoCo
• EMMA
• obsolete
• unit tests
• JaCoCo

56. Instrumentation Tests & Code Coverage
• has to be explicitly enabled
• gradle createDebugCoverageReport
• ${module}/build/reports/coverage/debug/index.html
• ${module}/build/outputs/code-coverage/connected/$
{deviceName}-coverage.ec
• doesn’t work on some devices!!!
buildTypes {
debug {
testCoverageEnabled true
}
}

57. JaCoCo

58. JaCoCo
• enabled by default for unit tests
• gradle test
• generates binary report in build/jacoco
• ${module}/build/jacoco/testDebugUnitTest.exec
• it’s necessary to create a JacocoReport task to obtain a readable
report

61. Good tests

62. Good tests
• run in any order
• run in isolation
• run consistently
• run fast
• are orthogonal

63. How to write testable apps?

64. Rules of thumb
• prefer pure Java
• abstract away from Android APIs
• separate business logic and UI
• don’t write business logic into activities and fragments
• MVP, MVVM is a way to go
• try avoid static and final
• use dependency injection

65. Questions?