<!DOCTYPE html>
<title>Test that rem units are responsive to animated font-size on root</title>
<link rel="help" href="https://drafts.csswg.org/css-animations/">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
  @keyframes font_size_animation {
    from { font-size: 10px; }
    to { font-size: 20px; }
  }
  :root {
    font-size: 1px;
    animation: font_size_animation steps(2, end) 1000s -500s;
  }

  #target1 {
    width: 1rem;
  }
</style>
<div id="target1"></div>
<script>
test(() => {
  assert_equals(getComputedStyle(target1).getPropertyValue('width'), '15px');
}, 'Animated font-size on root affects rem units');
</script>