css/css-animations/animation-base-response-004.html

<!DOCTYPE html>
<title>Tests that base responds to font-affecting properties appearing via setKeyframes</title>
<link rel="help" href="https://drafts.csswg.org/css-animations/">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
  #target1 {
    font-size: 10px;
    height: 1em;
  }
</style>
<div id=target1></div>
<script>
  test(function() {
    getComputedStyle(target1).height;

    let animation = target1.animate([
      { height: '50px' },
      { height: '100px' },
    ], {
      duration: 1000000,
      delay: -500000,
      easing: 'steps(2, end)'
    });

    assert_equals(getComputedStyle(target1).height, '75px');

    animation.effect.setKeyframes([
      { fontSize: '10px' },
      { fontSize: '20px' },
    ]);

    assert_equals(getComputedStyle(target1).height, '15px');
  }, 'Base is responsive to font-affecting appearing via setKeyframes');
</script>