css/css-animations/keyframes-rule-caching.html

<!DOCTYPE html>
<title>Tests that given two identical sheets containing the same @keyframes rule, modifying one sheet doesn't affect the other sheet</title>
<link rel="help" href="https://drafts.csswg.org/css-animations/#interface-csskeyframesrule">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style id="style1">
  @keyframes --anim {
    from { color: red; }
    to { color: black; }
  }
</style>
<style id="style2">
  @keyframes --anim {
    from { color: red; }
    to { color: black; }
  }
</style>
<script>
  test(() => {
    style1.sheet.cssRules[0].cssRules[1].style.color = "green";
    assert_equals(style1.sheet.cssRules[0].cssRules[1].style.color, "green", "sheet1 keyframe changed");
    assert_equals(style2.sheet.cssRules[0].cssRules[1].style.color, "black", "sheet2 keyframe did not change");
  }, "Modifying one sheet should not affect the other");
</script>