Android Testing Templates

Espresso is part of the Android Testing Support Library (ATSL) for writing reliable UI tests. The project utilizes several Espresso extensions:

• Espresso-Core: The fundamental API for testing state expectations, interactions, and assertions on the UI. It automatically synchronizes with the application UI state.
• Espresso-Contrib: Provides support for common Android widgets and extensions, such as RecyclerView.
• Espresso-Intents: Enables hermetic inter-app testing by allowing Intent verification and stubbing (similar to Mockito).
• Espresso-Web: Uses the WebDriver API to test and control WebView content on Android.

You can pass custom arguments to AndroidJUnitRunner using the -Pandroid.testInstrumentationRunnerArguments property in Gradle. This is useful for filtering tests by size, class, or passing arbitrary values to tests at runtime.

Examples

Run tests with a specific size qualifier (e.g., @Large):

./gradlew app:connectedAndroidTest -Pandroid.testInstrumentationRunnerArguments.size=large

Run a specific test class:

./gradlew app:connectedAndroidTest -Pandroid.testInstrumentationRunnerArguments.class=com.example.android.testing.blueprint.ui.espresso.EspressoTest

Pass an arbitrary argument to be accessed at runtime:

./gradlew module-flavor1-androidTest-only:connectedAndroidTest -Pandroid.testInstrumentationRunnerArguments.argument1=make_test_fail

Unit tests (local tests) run on your development machine's JVM.

In Android Studio

1. Open the Build Variants window and ensure Unit Tests is selected.
2. Open a local test class (e.g., LocalUnitTest.java).
3. Right-click the class and select Run as JUnit test.

Via Gradle (Command Line)

• Run all unit tests in the app module:

  ./gradlew app:test

• Run all unit tests in a specific module:

  ./gradlew :{module}:test

• Run filtered unit tests (by package/class): Note: You cannot use --tests with ./gradlew app:test. You must use the specific variant task.

  ./gradlew :app:testFlavor1DebugUnitTest --tests "com.example.android.testing.blueprint.*"

  In a project without flavors:

  ./gradlew :{module}:testDebugUnitTest --tests {test-filter}

Instrumentation tests run on a physical device or emulator. You can execute them via Android Studio or the command line.

In Android Studio

1. Open the Build Variants window and ensure Android Instrumentation Tests is selected.
2. Open an instrumentation test class (e.g., EspressoTest.java).
3. Right-click the class and select Run as Android Test.

Via Gradle (Command Line)

To run all instrumentation tests in the app module:

./gradlew app:connectedAndroidTest

Via adb (Command Line)

1. Install both the app and the test APK:

./gradlew app:installFlavor2Debug app:installFlavor2DebugAndroidTest

2. Execute the instrumentation command:

adb shell am instrument -w com.example.android.testing.blueprint.flavor2.test/android.support.test.runner.AndroidJUnitRunner

Unit Test Coverage

• Android Studio: Use the Run test with code coverage option. Reports appear next to lines in the editor.
• Gradle (JaCoCo): To generate HTML reports for a Java module:

  ./gradlew module-plain-java:test module-plain-java:jacocoTestReport

  The report is located at: module-plain-java/build/reports/jacoco/test/html/index.html

Android Test Coverage

• Coverage reports for instrumentation tests are located in: app/build/reports/coverage.

You can pass custom arguments to AndroidJUnitRunner via Gradle using the -Pandroid.testInstrumentationRunnerArguments property. This is useful for filtering specific tests or passing runtime flags to your tests.

Examples

• Run tests with a specific size qualifier (e.g., @Large):

  ./gradlew app:connectedAndroidTest -Pandroid.testInstrumentationRunnerArguments.size=large

• Run a specific test class:

  ./gradlew app:connectedAndroidTest -Pandroid.testInstrumentationRunnerArguments.class=com.example.android.testing.blueprint.ui.espresso.EspressoTest

• Pass an arbitrary argument to be accessed at runtime:

  ./gradlew module-flavor1-androidTest-only:connectedAndroidTest -Pandroid.testInstrumentationRunnerArguments.argument1=make_test_fail