com.facebook.testing.screenshot:layout-hierarchy-litho

Screenshot Tests for Android

screenshot-tests-for-android is a library that can generate fast deterministic screenshots while running instrumentation tests on Android.

We mimic Android's measure(), layout() and draw() to generate screenshots on the test thread. By not having to do the rendering on a separate thread we have control over animations and handler callbacks which makes the screenshots extremely deterministic and reliable for catching regressions in continuous integration.

We also provide utilities for using screenshot tests during the development process. With these scripts you can iterate on a view or layout and quickly see how the view renders in a real Android environment, without having to build the whole app. You can also render the view in multiple configurations at one go.

Documentation

Take a look at the documentation at http://facebook.github.io/screenshot-tests-for-android/#getting-started

Requirements

screenshot-tests-for-android is known to work with MacOS or Linux.

The host tooling probably doesn't work on Windows, but can be made to work with a little effort. We'll happily accept pull requests!

You need python-2.7 for the gradle plugin to work, and we also recommending installing the python-pillow library which is required for recording and verifying screenshots.

Building screenshot-tests-for-android

You don't have to build screenshot-tests-for-android from scratch if you don't plan to contribute. All artifacts are available from Maven Central.

If you plan to contribute, this is the code is broken up into a few modules:

• The core module is packaged as part of your instrumentation tests and generates screenshots on the device.

• The plugin module adds Gradle tasks to make it easier to work with screenshot tests.

• The layout-hierarchy-common module adds extra common View information to your reports' layout hierarchy viewer

• The layout-hierarchy-litho module adds extra Litho component information to your reports' layout hierarchy viewer

In addition you'll find python code inside plugin/src/py. This code is packaged into the gradle plugin.

We have tests for the python code and the core library. Run these commands to run all the tests:

  $ gradle :plugin:pyTests
  $ gradle :core:connectedAndroidTest

Both need a running emulator.

Python tests rely on the mock and Pillow libraries. Both can be installed via pip install mock and pip install Pillow.

You can install all the artifacts to your local maven repository using

  $ gradle installArchives

Running With a Remote Service

For usage with a remote testing service (e.g. Google Cloud Test Lab) where ADB is not available directly the plugin supports a "disconnected" workflow. Collect all screenshots into a single directory and run the plugin using the following options

Example

The location of the screenshot artifacts can be configured in the project's build.gradle:

  screenshots {
      // Points to the directory containing all the files pulled from a device
      referenceDir = path/to/screenshots
  }

Then, screenshots may be verified by executing the following:

  $ gradle :<project>:verify<flavor>ScreenshotTest

To record, simply change verify to record.

Contributing

Please see the contributing file.

Authors

screenshot-tests-for-android was originally written by Arnold Noronha ([e-mail]) You can reach him at @tdrhq on GitHub.

It is currently maintained by Hilal Alsibai (@xiphirx)

License

screenshot-tests-for-android is Apache-2-licensed.