The Flutter Engine performs rudimentary pixel tests in its unit-test harnesses (shell_unittests, embedder_unittests). Since these unit-tests are for subsystems that don't necessarily care about how Flutter uses Skia, they usually rely more on asserting the correctness of internal data structures rather than check the pixels generated.

A full featured pixel test harness that comprehensively exercises dart:ui features is desired to catch regressions caused by changes to the way in which the engine uses Skia APIs.

Per @Piinks, an unused Skia Gold instance exists for the engine already at https://flutter-engine-gold.skia.org/ which can be used as the basis for this new test harness. the flutter_goldens package performs these tests for the framework instance and may be adapted for use with the engine.

Like the other harnesses, it may not depend on the framework itself and tests will be written using just the dart:ui APIs. A single can be used to run all cases and upload them to the Gold instance.