css/cssom/set-selector-text-attachment.html

<!DOCTYPE html>
<title>Setting selectorText does not detach rule</title>
<link rel="help" href="https://drafts.csswg.org/cssom-1/#dom-cssstylerule-selectortext">
<link rel="help" href="https://issues.chromium.org/issues/396612327">
<script src=/resources/testharness.js></script>
<script src=/resources/testharnessreport.js></script>
<style id=sheet>
  span {
    color: black;
  }
</style>
<div>
  <span id=span>A</span>
</div>
<script>
  test(() => {
    let rule = sheet.sheet.cssRules[0];
    let style = rule.style;

    style.color = 'red';
    assert_equals(getComputedStyle(span).color, 'rgb(255, 0, 0)');

    rule.selectorText = '#span';

    style.color = 'green';
    assert_equals(getComputedStyle(span).color, 'rgb(0, 128, 0)');
  }, 'Modifying property value invalidates style, even after selectorText mutation');
</script>