run_tests.py does not appear to be checking the number of errors or the errors themselves for the tokenizer, encoding or serializer tests from html5lib-tests -

run_tests.py does not appear to be checking the number of errors or the errors themselves for the tokenizer, encoding or serializer tests from html5lib-tests - which represent the majority of tests. There's also something off about your benchmark comparison. If one runs pytest on html5lib, which uses html5lib-test plus its own unit tests and does check if errors match exactly, the pass rate appears to be much higher than 86%: $ uv run pytest -v 17500 passed, 15885 skipped, 683 xfailed, These numbers are inflated because html5lib-tests/tree-construction tests are run multiple times in different configurations. Many of the expected failures appear to be script tests similar to the ones JustHTML skips.