<!DOCTYPE html>
<link rel="help" href="https://drafts.csswg.org/scroll-animations-1/#animation-timeline">
<link rel="help" href="https://drafts.csswg.org/css-animations-1/#keyframes">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
</head>
<style>
  @keyframes test {
    from { width: 100px; animation-timeline: --foo; }
    to { width: 100px; animation-timeline: --foo; }
  }
  #target {
    width: 50px;
    animation-name: test;
    animation-duration: 1s;
    animation-play-state: paused;
  }
</style>
<div id="target"></div>
<script>
test(() => {
  let style = getComputedStyle(document.getElementById('target'));
  // Checking 'width' verifies that the animation is applied at all.
  assert_equals(style.width, '100px');
  assert_equals(style.animationTimeline, 'auto');
}, 'The animation-timeline property may not be used in keyframes');
</script>
