css/selectors/user-invalid.html

<!doctype html>
<title>Support for the :user-invalid pseudo-class</title>
<link rel="help" href="https://drafts.csswg.org/selectors/#user-pseudos">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<input value="bar" pattern="foo">
<script>
test(() => {
  const input = document.querySelector('input');
  assert_false(input.validity.valid, "Should be invalid");
  // The selector can't match because no interaction has happened.
  assert_false(input.matches(':user-invalid'));
}, ':user-invalid selector should be supported');

// historical: https://github.com/w3c/csswg-drafts/issues/1329
test(() => {
  const input = document.querySelector('input');
  // matches() will throw if the selector isn't suppported
  assert_throws_dom("SyntaxError", () => input.matches(':user-error'));
}, ':user-error selector should not be supported');
</script>