Docs on Blink layout tests seems outdated

https://v8.dev/docs/blink-layout-tests

I’m having troubles with the third point (rebaselining the tests in Chromium), if you try to commit [ NeedsRebaseline ] it will fail during presubmit checks (as you can see here).

Another document exists with a manual way to do it (which is known to work): https://chromium.googlesource.com/chromium/src/+/master/docs/testing/web_tests.md#Rebaselining-Web-Tests.

Status: I’m currently following it and I can report the result here.

[MayaLekova]

@xtuc Please check whether my last commit reflects the experience that you had. Once your CL in Chromium lands, I’d be happy to also link it in the docs as an example, that’s a great idea!

Re:

• I would expect the tools/run_web_tests.py --reset-results flag to update the TestExpectations file, however it doesn’t.

AFAIK, the automatic updating of the TestExpectations file will work only when you make changes in Chromium itself, not in V8, because we can’t synchronize rolling V8 into Chromium with this update. That’s why we fall back to the manual process and you need to do the whole skip-unskip dance with the TestExpectations file.

[mathiasbynens]

https://bugs.chromium.org/p/chromium/issues/detail?id=735176 seems relevant:

Pretty soon, NeedsRebaseline will be removed (bug 692811).

Now there’s NeedsManualRebaseline and Rebaseline. In practice, what these actually mean is:

• NeedsManualRebaseline means “run the test but ignore the results”
• Rebaseline means “select this test when webkit-patch rebaseline-expectations is run”