Summary

Now that we've started to bring the DevTools testing into core we can start to make them even stronger :)

Miscellaneous thoughts:

• Move LighthouseTestRunner into core as well so we can make changes to the shared utilities.
• Strengthen audit assertions, for example we had to disable all perf assertions in the past because screenshots were flaky. It would be awesome if we could flip the script to get Chromium's perspective to consider flaky screenshot collection a bug and fix that instead of disabling the tests that point it out 😃
• Assertions on the rendering of the report. AFAIK all our current tests assert on the LHR are obtained from a spy on internal methods. Some sort of testing that the complete rendering pipeline works would be great for testing PRs like clients(devtools): update report-generator.js to match DevTools changes #11411
• A package.json script that would build and open the latest Lighthouse in DevTools for manual inspection.
• fix caching TTL DevTools webtests improvements #11414 (comment)
• remove the TestExpectations that marks one of the tests flaky (probably not flaky anymore)
• startup errors should show error and not timeout i18n: use IcuMessage objects instead of string IDs #10630 (comment)
• only put explanation in snapshots when audit fails
• don't hide output of http server (blocked port hangs)
• git pull devtools checkout in .tmp tests: refresh devtools checkout for webtests #11717 lighthouse-export-run.js silent failure #11678