It intentionally has no dependencies on the Flutter framework or tooling, such that it should be buildable as a presubmit or postsubmit to the engine even in the face of changes to Dart or dart:ui that require upstream changes in the Flutter tooling.

Adding a New Scenario

Create a new subclass of Scenario and add it to the map in scenarios.dart. For an example, see animated_color_square.dart, which draws a continuously animating colored square that bounces off the sides of the viewport.

Then set the scenario from the Android or iOS app by calling "set_scenario" on platform channel.

Running for iOS

./build_and_run_ios_tests.sh

iOS Platform View Tests

For PlatformView tests on iOS, you'll also have to edit the dictionaries in AppDelegate.m and GoldenTestManager.m so that the correct golden image can be found. Also, you'll have to add a GoldenPlatformViewTests in PlatformViewUITests.m.

If PlatformViewRotation is failing, make sure Simulator app Device > Rotate Device Automatically is selected, or run:

defaults write com.apple.iphonesimulator RotateWindowWhenSignaledByGuest -int 1

Generating Golden Images on iOS

Screenshots are saved as XCTAttachment's. If you look at the output from running the tests you'll find a path in the form: /Users/$USER/Library/Developer/Xcode/DerivedData/Scenarios-$HASH. Inside that directory you'll find ./Build/Products/Debug-iphonesimulator/ScenariosUITests-Runner.app/PlugIns/ScenariosUITests.xctest/ which is where all the images that were compared against golden reside.

Running for Android

The test is run on a x86 emulator. To run the test locally, you must create an emulator running API level 28, using an x86_64 ABI, and set the following screen settings in the avd's config.ini file:

hw.lcd.density = 480
hw.lcd.height = 1680
hw.lcd.width = 1080
lcd.depth = 16

This file is typically located in your $HOME/.android/avd/<avd> folder.

Once the emulator is up, you can run the test by running:

./build_and_run_android_tests.sh

Generating Golden Images on Android

In the android directory, run:

./gradlew app:recordDebugAndroidTestScreenshotTest

The screenshots are recorded into android/reports/screenshots.

Verifying Golden Images on Android

In the android directory, run:

./gradlew app:verifyDebugAndroidTestScreenshotTest

Changing dart:ui code

If you change the dart:ui interface, remember to point the sky_engine and sky_services clauses to your local engine's output path before compiling.