Tracking bug for testing improvements

[elliette]

CI improvements (reduce time it takes for Github actions to run):

• DWDS tests should be sharded into groups (currently they take much longer than the other CI actions)
  • Completed in Shard DWDS tests and fix CI test flakiness #1851
• Move tests with a large timeout limit (eg, the devtools _test at 5 minutes) to a cron job (tracked in Tests with long timeouts should be moved to a cron job  #1846)
• All tests should have a timeout set
  • Completed in Add test timeout of 2 minutes for all tests missing a timeout #1854

Refactor TestContext setup:

• Make TestServer more re-usable (described in Make DWDS test server more re-usable #1779)
• Make it clearer what parameters should be passed to TestContext (eg, it is unclear the difference between path vs pathToServe). Also the default Dart entry file is in append_body, but the default HTML entry file is in hello_world.
  • Completed in Refactor TestContext constructor for clarity #1844 and Tests should servemain.dart and index.html from the same directory #1856
• Currently a lot of the fields in TestContext are late, because they are only initialized after TestContext.setUp() is called. I think it would make more sense to have two separate classes for test setup: TestPackage which is equivalent to TestContext , and TestContext which is equivalent to TestContext.setUp().

Other improvements:

• Callstack tests break if test fixtures are formatted (described in Call stack tests break if main.dart in fixtures/_testPackageSound / fixtures/_testPackage is formatted #1831)
  • Fixed in fix format breaking tests #2124
• All packages should have a mono_pkg.yml file, so that the analyze and format steps can be run against them during CI
• Support Dart 3.0 breaking changes in tests (tracked in Support tests with breaking changes in Dart 3.0.0 #1818)
• Switch to using puppeteer for all integration tests (tracked in Switch to using puppeteer instead of WebDriver for all integration tests  #1847)
• dwds/test/fixtures directory contains dill files (used for testing) along with utilities.dart (test utilities) and context.dart (test setup). This should be reorganized.