css/css-nesting/invalidation-004.html

<!doctype html>
<title>CSS Selectors nested invalidation through @media by selectorText</title>
<link rel="author" title="Steinar H. Gunderson" href="mailto:sesse@chromium.org">
<link rel="help" href="https://drafts.csswg.org/css-nesting-1/">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<style>
  .b {
    color: red;
  }
  & {
    @media screen {
      &.b { color: green; }
    }
  }
</style>

<div id="elem" class="a b">
  Test passes if color is green.
</div>

<script>
  test(() => {
    let elem = document.getElementById('elem');
    assert_equals(getComputedStyle(elem).color, 'rgb(255, 0, 0)');
    document.styleSheets[0].rules[1].selectorText = '.a';
    assert_equals(getComputedStyle(elem).color, 'rgb(0, 128, 0)');
  });
</script>