Yegor 954f1988c5
Add custom test plugin that supports screenshot tests (#12079)
- Add a custom `PlatformPlugin` that spins up a server waiting for test to request a screenshot.
  - When a screenshot is requested the plugin talks to Chrome via the debug port, captures a screenshot, and compares it with a golden file
- This PR also adds proper CLI for `dev/test.dart` with an `ArgParser` for future extension into a proper developer tool for the team.
  - As a first couple of features, it adds `--debug` option to launch Chrome in debug mode, a `--target` option to choose a single test to run rather than all tests, and `--shard` option to choose a subset of tests to run.

Limitations:
 - While screenshot test will run on Cirrus, they are configured to not fail on Cirrus. Need to solve Chrome version skew.
 - Stack maps do not work yet (you get stacks, but they are nonsensical)
 - When requesting a single test, build_runner builds all tests anyway
 - Nothing but desktop Chrome is supported
 - Nothing but Linux is supported
 - There's no Chrome version pinning; currently assumed stable Chrome channel
2019-09-10 13:53:47 -07:00
..
2019-08-09 11:11:20 -07:00