The Android Testing Support Library provides an extensive framework for testing Android apps. This library provides a set of APIs that allow you to quickly build and run test code for your apps, including JUnit 4 and functional user interface (UI) tests. You can run tests created using these APIs from the Android Studio IDE or from the command line.
Continue to the [https://google.github.com/android-testing-support-library](ATSL documentation page).
The ATSL documentation page is hosted on GitHub Pages and contributions are welcome. Check out the gh-pages branch.
The ATSL is part of AOSP and can be found in the platform/frameworks/testing directory.