No, they're immediately provably worse. If you started work on a CSS rasterizer today, there are zero test suites you can use for reference comparison.

I'm talking about easy stuff, too, like normal flow, margin, border, padding box alignment.

The existing official test suites are entirely manual.

Edit: What you're describing requires you to make the entire world first, then finally test something.

Here's an example: I want to test the white-space property. How do I test that? Oh also, font rasterizers are all different and standards don't dictate what happens after box layout. It's acceptable that glyphs render with different dimensions.

How do I test that? A casual HN reader isn't going to care. Someone actually writing this stuff, will.