> but many of them require JS to perform the check

Yeah, if we add JS support to Blitz then one of our initial targets will probably be "enough to run the WPT test runner".

> I was also reading how you do it in blitz

We are able to run ~20k tests (~30k subtests) from the `css` directory without JS which is IMO more than enough for it to be worthwhile.

> Probably the best indicator of which features are supported is to pass as many tests as possible from WPT that cover that feature.

Yes, and no. It definitely is an indicator to some extent. But in implementing floats recently I've a lot of the web suddenly renders correctly, but I'm only passing ~100 more tests!