JUnit4 rules with AndroidX Test

AndroidX Test includes a set of JUnit rules to be used with the AndroidJUnitRunner. JUnit rules provide more flexibility and reduce the boilerplate code required in tests. For example, they can be used to start a specific activity.

ActivityScenarioRule

This rule provides functional testing of a single activity. The rule launches the chosen activity before each test annotated with @Test, as well as before any method annotated with @Before. The rule terminates the activity after the test completes and all methods annotated with @After finish. To access the given activity in your test logic, provide a callback runnable to ActivityScenarioRule.getScenario().onActivity().

The following code snippet demonstrates how to incorporate ActivityScenarioRule into your testing logic:

Kotlin

@RunWith(AndroidJUnit4::class.java)
@LargeTest
class MyClassTest {
  @get:Rule
  val activityRule = ActivityScenarioRule(MyClass::class.java)

  @Test fun myClassMethod_ReturnsTrue() {
    activityRule.scenario.onActivity { … } // Optionally, access the activity.
   }
}

Java

public class MyClassTest {
    @Rule
    public ActivityScenarioRule<MyClass> activityRule =
            new ActivityScenarioRule(MyClass.class);

    @Test
    public void myClassMethod_ReturnsTrue() { ... }
}

ServiceTestRule

This rule provides a simplified mechanism to launch your service before the tests and shut it down before and after. You can start or bind the service with one of the helper methods. It automatically stops or unbinds after the test completes and any methods annotated with @After have finished.

Kotlin

@RunWith(AndroidJUnit4::class.java)
@MediumTest
class MyServiceTest {
  @get:Rule
  val serviceRule = ServiceTestRule()

  @Test fun testWithStartedService() {
    serviceRule.startService(
      Intent(ApplicationProvider.getApplicationContext<Context>(),
      MyService::class.java))
    // Add your test code here.
  }

  @Test fun testWithBoundService() {
    val binder = serviceRule.bindService(
      Intent(ApplicationProvider.getApplicationContext(),
      MyService::class.java))
    val service = (binder as MyService.LocalBinder).service
    assertThat(service.doSomethingToReturnTrue()).isTrue()
  }
}

Java

@RunWith(AndroidJUnit4.class)
@MediumTest
public class MyServiceTest {
    @Rule
    public final ServiceTestRule serviceRule = new ServiceTestRule();

    @Test
    public void testWithStartedService() {
        serviceRule.startService(
                new Intent(ApplicationProvider.getApplicationContext(),
                MyService.class));
        // Add your test code here.
    }

    @Test
    public void testWithBoundService() {
        IBinder binder = serviceRule.bindService(
                new Intent(ApplicationProvider.getApplicationContext(),
                MyService.class));
        MyService service = ((MyService.LocalBinder) binder).getService();
        assertThat(service.doSomethingToReturnTrue()).isTrue();
    }
}

Additional resources

For more information about using JUnit rules in Android tests, consult the following resources.

Documentation

Samples