Testing

AndroidX contains unit and integration tests that are run automatically when a change is uploaded. It also contains a number of sample applications that are useful for demonstrating how to use features as well as performing manual testing.

Adding tests

For an example of how to set up simple unit and integration tests in a new module, see aosp/1189799. For an example of how to set up Espresso-powered integration tests, see the preference library's build.gradle and EditTextPreferenceTest.java files.

The currently allowed test runners for on-device tests are AndroidJUnitRunner and Parameterized.

NOTE All package/class/method combinations must be unique. Multiple copies of the same class/method can be included e.g. under different directories, but must be distinguishable by their packages.

NOTE For best practices on writing libraries in a way that makes it easy for end users -- and library developers -- to write tests, see the Testability guide.

What gets tested, and when

We use the AffectedModuleDetector to determine what projects have changed since the last merge.

In presubmit, “affected” modules will run all host and device tests regardless of size. Modules that depend on affected modules will run all host tests, but will only run device tests annotated with @SmallTest or @MediumTest.

When changes are made that can't be associated with a module, are in the root of the checkout, or are within buildSrc, then all host tests and all device tests annotated with @SmallTest or @MediumTest will be run for all modules.

Presubmit tests represent only a subset of the devices on which our tests run. The remaining devices are tested only in postsubmit. In postsubmit, all host and device tests are run for all modules.

Test annotations

Test size and runners

All device tests should be given a size annotation, which is one of:

• @SmallTest
• @MediumTest
• @LargeTest

If a device test is not annotated with its size, it will be run as if it were @LargeTest by default. Host tests do not need to be annotated with their size, as all host tests are run regardless of size.

This annotation can occur at either the class level or individual test level.

Annotation	Max duration
@SmallTest	200ms
@MediumTest	1000ms
@LargeTest	100000ms

Disabling tests

To disable a device-side test in presubmit testing only -- but still have it run in postsubmit -- use the @FlakyTest annotation. There is currently no support for presubmit-only disabling of host-side tests.

If you need to stop a host- or device-side test from running entirely, use JUnit‘s @Ignore annotation. Do not use Android’s @Suppress annotation, which only works with Android test runners and will not work for host-side tests.

Filtering devices

To restrict a test to a range of SDKs, use @SdkSuppress which allows specifying a range with minSdkVersion and maxSdkVersion. This annotation also supports targeting a specific pre-release SDK with the codeName parameter.

// Target SDKs 17 through 19, inclusive
@SdkSuppress(minSdkVersion = 17, maxSdkVersion = 19)

// Target pre-release SDK T only
@SdkSuppress(minSdkVersion = Build.VERSION_CODES.TIRAMISU, codeName = "Tiramisu")

You may also gate portions of test implementation code using SDK_INT or BuildCompat.isAtLeast methods. s To restrict to only physical devices, use @RequiresDevice.

NOTE Cuttlefish is not affected by this annotation, only e.g. Studio emulators. If Cuttlefish is displaying behavior that differs from a physical device, they are considering that a bug in Cuttlefish, so please file those bugs instead of only looking for a workaround.

Animations in tests

Animations are disabled for tests by default. This helps avoid flakes due to timing and also makes tests faster.

In rare cases, like testing the animations themselves, you may want to enable animations for a particular test or test class. For those cases, you can use the AnimationDurationScaleRule.

Robolectric

Robolectric tests are supported in AndroidX; however, if you targeting a pre-release version of the Android SDK then you may see an error like

java.lang.IllegalArgumentException: Package targetSdkVersion=31 > maxSdkVersion=30
at org.robolectric.plugins.DefaultSdkPicker.configuredSdks(DefaultSdkPicker.java:118)
at org.robolectric.plugins.DefaultSdkPicker.selectSdks(DefaultSdkPicker.java:69)

You can force Robolectric to run using an earlier version of the platform SDK by creating a <project>/src/test/resources/robolectric.properties file with the following contents:

# Robolectric currently doesn't support API 31, so we have to explicitly specify 30 as the target
# sdk for now. Remove when no longer necessary.
sdk=30

Using the emulator

You can use the emulator or a real device to run tests. If you wish to use the emulator, you will need to access the AVD Manager (and your downloaded emulator images) using a separate “normal” instance of Android Studio. “Normal” means a non-Canary build of Studio that you would use for regular app development -- the important part being that it points to the Android SDK where your downloaded emulator images reside. You will need to open a project to get the Tools menu -- do NOT open the AndroidX project in the “normal” instance of Android Studio; instead, open a normal app or create a blank project using the app wizard.

NOTE You can reuse the emulator and system images from a “normal” installation of Android Studio by linking the emulator and system_images directories to a standard Android SDK path and restarting Android Studio. This is set up automatically by studiow on Google-managed devices with a standard Android SDK path. In other cases, it may be set up manually with something like: cd prebuilts/fullsdk-darwin ln -s ~/Library/Android/sdk/emulator emulator ln -s ~/Library/Android/sdk/system-images system-images (substituting fullsdk-linux and your local SDK path as appropriate)

Debugging with platform SDK sources

The platform SDK sources that are checked into the development branch may not match up with the build of Android present on the emulator or your physical device. As a result, the line numbers reported by the debugger may not match up the actual code being run.

If you have a copy of the sources for the build against which you are debugging, you can manually specify your platform SDK source path:

1. Click on a module (e.g. appcompat) in the Project view
2. Press Ctrl-Shift-A and type “Module Settings”, then run the action
3. In the Project Structure dialog, navigate to SDKs > Android API 29 Platform > Sourcepath
4. Use the - button to remove any paths that are present, then use the + button to add the desired source path, ex. <android checkout root>/frameworks/base if you are debugging against a locally-built system image

NOTE The Project Structure dialog reachable via File > Project Structure is not the same as the Project Structure dialog that will allow you to specify the SDK source path. You must use the “Module Settings” action as directed above.

Running unit and integration tests

From Android Studio, right-click can be used to run most test targets, including source files, classes within a file, or individual test methods but not entire modules. To run a supported test target, right-click on the test target and then click Run <name of test target>.

To run tests for an entire module such as appcompat, use Run -> Edit configurations... and use the + button to create a new Android Instrumented Tests configuration. Specify the module to be tested, give it a reasonable name (not “All Tests”) and click OK, then use the Run menu to run the configuration.

NOTE If you receive the error JUnit version 3.8 or later expected this means that Android Studio generated an Android JUnit configuration when you actually needed an Android Instrumented Tests configuration. Open the Run -> Edit configurations... dialog and delete the configuration from Android JUnit, then manually add a configuration in Android Instrumented Tests.

From the command line

Following a successful build, tests may be run against a particular AndroidX module using gradlew.

To run all unit or integration tests in a specific project, run the following from framework/support:

# Run instrumentation tests on a connected device
./gradlew <project-name>:connectedAndroidTest --info --daemon

# Run local unit tests
./gradlew <project-name>:test --info --daemon

substituting the Gradle project name (ex. core).

To run all integration tests in the specific project and test class you're working on, run

./gradlew <project-name>:connectedAndroidTest --info --daemon \
    -Pandroid.testInstrumentationRunnerArguments.class=<fully-qualified-class>[\#testName]

substituting the Gradle project name (ex. viewpager) and fully-qualified class name (ex. androidx.viewpager.widget.ViewPagerTest) of your test file, optionally followed by \#testName if you want to execute a single test in that file. Substitute test for connectedAndroidTest to run local unit tests.

If you see some weird compilation errors such as below, run ./gradlew clean first:

Unknown source file : UNEXPECTED TOP-LEVEL EXCEPTION:
Unknown source file : com.android.dex.DexException: Multiple dex files define Landroid/content/pm/ParceledListSlice$1;

Test apps

Library developers are strongly encouraged to write test apps that exercise their library's public API surface. Test apps serve multiple purposes:

• Integration testing and validation of API testability, when paired with tests
• Validation of API usability and developer experience, when paired with a use case or critical user journey
• Sample documentation, when embedded into API reference docs using the @sample and @Sampled annotations

Legacy test apps

We have a set of legacy sample Android applications in projects suffixed with -demos. These applications do not have tests and should not be used as test apps for new APIs, but they may be useful for manual regression testing.

1. Click Run/Debug Configuration on the top of the window.
2. Select the app you want to run.
3. Click ‘Run’ button.

Benchmarking

AndroidX supports benchmarking - locally with Studio/Gradle, and continuously in post-submit. For more information on how to create and run benchmarks, see Benchmarking.