AndroidJUnitRunner

The AndroidJUnitRunner class is a JUnit test runner that lets you run JUnit 3- or JUnit 4-style test classes on Android devices, including those using the Espresso and UI Automator testing frameworks.

The test runner handles loading your test package and the app under test to a device, running your tests, and reporting test results. This class replaces the InstrumentationTestRunner class, which only supports JUnit 3 tests.

This test runner supports several common testing tasks, including the following:

• Writing JUnit tests
• Accessing instrumentation information
• Filtering tests
• Sharding tests

Write JUnit tests

The test runner is compatible with your JUnit 3 and JUnit 4 (up to JUnit 4.10) tests. However, you should avoid mixing JUnit 3 and JUnit 4 test code in the same package, as this might cause unexpected results. If you are creating an instrumented JUnit 4 test class to run on a device or emulator, your test class must be prefixed with the @RunWith(AndroidJUnit4.class) annotation.

The following code snippet shows how you might write an instrumented JUnit 4 test to validate that the changeText operation in the ChangeTextBehavior class works correctly:

@RunWith(AndroidJUnit4::class)
@LargeTest
class ChangeTextBehaviorTest {
    val stringToBeTyped = "Espresso"
    @get:Rule
    val activityRule = ActivityTestRule(MainActivity::class.java)

    @Test fun changeText_sameActivity() {
        // Type text and then press the button.
        onView(withId(R.id.editTextUserInput))
            .perform(typeText(stringToBeTyped), closeSoftKeyboard())
        onView(withId(R.id.changeTextBt)).perform(click())

        // Check that the text was changed.
        onView(withId(R.id.textToBeChanged))
            .check(matches(withText(stringToBeTyped)))
    }
}

@RunWith(AndroidJUnit4.class)
@LargeTest
public class ChangeTextBehaviorTest {

    private static final String stringToBeTyped = "Espresso";

    @Rule
    public ActivityTestRule<MainActivity> activityRule =
            new ActivityTestRule<>(MainActivity.class);

    @Test
    public void changeText_sameActivity() {
        // Type text and then press the button.
        onView(withId(R.id.editTextUserInput))
                .perform(typeText(stringToBeTyped), closeSoftKeyboard());
        onView(withId(R.id.changeTextBt)).perform(click());

        // Check that the text was changed.
        onView(withId(R.id.textToBeChanged))
                .check(matches(withText(stringToBeTyped)));
    }
}

Use Android Test Orchestrator

When using AndroidJUnitRunner version 1.0 or higher, you have access to a tool called Android Test Orchestrator, which allows you to run each of your app's tests within its own invocation of Instrumentation.

Android Test Orchestrator offers the following benefits for your testing environment:

• Minimal shared state. Each test runs in its own Instrumentation instance. Therefore, if your tests share app state, most of that shared state is removed from your device's CPU or memory after each test.

  To remove all shared state from your device's CPU and memory after each test, use the clearPackageData flag.

• Crashes are isolated. Even if one test crashes, it takes down only its own instance of Instrumentation, so the other tests in your suite still run.

Both Android Studio and Firebase Test Lab have Android Test Orchestrator pre-installed, though you need to enable the feature in Android Studio.

If you use a different toolchain to test your app, however, you can still use Android Test Orchestrator by completing the following steps:

1. Include the necessary packages in your app's build file.
2. Enable Android Test Orchestrator from the command-line.

Enable from Gradle

To enable Android Test Orchestrator using the Gradle command-line tool, complete these steps:

1. Add the following statements to your project's build.gradle file:

   android {
     defaultConfig {
      ...
      testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
   
      // The following argument makes the Android Test Orchestrator run its
      // "pm clear" command after each test invocation. This command ensures
      // that the app's state is completely cleared between tests.
      testInstrumentationRunnerArguments clearPackageData: 'true'
    }
   
     testOptions {
       execution 'ANDROIDX_TEST_ORCHESTRATOR'
     }
   }
   
   dependencies {
     androidTestImplementation 'androidx.test:runner:1.1.0'
     androidTestUtil 'androidx.test:orchestrator:1.1.0'
   }

2. Run Android Test Orchestrator by executing the following command:

   ./gradlew connectedCheck

Enable from Android Studio

Support for Android Test Orchestrator is available with Android Studio 3.0 and higher. To enable Android Test Orchestrator in Android Studio, add the statements shown in Enable from Gradle to your app's build.gradle file.

Enable from command line

To use Android Test Orchestrator on the command line, run the following commands in a terminal window:

# Install the test orchestrator.
adb install -r path/to/m2repository/com/androidx/test/orchestrator/1.1.0/orchestrator-1.1.0.apk

# Install test services.
adb install -r path/to/m2repository/com/androidx/test/services/test-services/1.1.0/test-services-1.1.0.apk

# Replace "com.example.test" with the name of the package containing your tests.
# Add "-e clearPackageData true" to clear your app's data in between runs.
adb shell 'CLASSPATH=$(pm path androidx.test.services) app_process / \
  androidx.test.services.shellexecutor.ShellMain am instrument -w -e \
  targetInstrumentation com.example.test/androidx.test.runner.AndroidJUnitRunner \
  androidx.test.orchestrator/.AndroidXTestOrchestrator'

As the command syntax shows, you install Android Test Orchestrator, then use it directly.

adb shell pm list instrumentation

Architecture

The Orchestrator service APK is stored in a process that's separate from the test APK and the APK of the app under test, as shown in Figure 1:

Android Test Orchestrator collects JUnit tests at the beginning of your test suite run, but it then executes each test separately, in its own instance of Instrumentation.

Access the app context

To get the context for the app under test, call the static ApplicationProvider.getApplicationContext() method. If you've created a custom subclass of Application in your app, this method returns your custom subclass's context.

If you're a tools implementer, you can access low-level testing APIs using the InstrumentationRegistry class. This class includes the Instrumentation object, the target app Context object, the test app Context object, and the command line arguments passed into your test. This data is useful when you are writing tests using the UI Automator framework or when your tests depend on the app's context.

Filter tests

In your JUnit 4.x tests, you can use annotations to configure the test run. This feature minimizes the need to add boilerplate and conditional code in your tests. In addition to the standard annotations supported by JUnit 4, the test runner also supports Android-specific annotations, including the following:

• @RequiresDevice: Specifies that the test should run only on physical devices, not on emulators.
• @SdkSupress: Suppresses the test from running on a lower Android API level than the given level. For example, to suppress tests on all API levels lower than 23 from running, use the annotation @SDKSupress(minSdkVersion=23).
• @SmallTest, @MediumTest, and @LargeTest: Classify how long a test should take to run, and consequently, how frequently you can run the test.

Shard tests

The test runner supports splitting a single test suite into multiple shards, so you can easily run tests belonging to the same shard together as a group, under the same Instrumentation instance. Each shard is identified by an index number. When running tests, use the -e numShards option to specify the number of separate shards to create and the -e shardIndex option to specify which shard to run.

For example, to split the test suite into 10 shards and run only the tests grouped in the second shard, use the following command:

adb shell am instrument -w -e numShards 10 -e shardIndex 2

More information

To learn more about using this test runner, see the API reference.

To use the AndroidJUnitRunner class, include it as one of your project's packages, as described in set up project for AndroidX Test.

Additional resources

For more information about using AndroidJUnitRunner, consult the following resources.

Samples

• AndroidJunitRunnerSample: Showcases test annotations, parameterized tests, and test suite creation.