scroll-animations/css/scroll-timeline-default.html

<!DOCTYPE HTML>
<html class="reftest-wait">
<title>The default scroll() timeline</title>
<link rel="help" href="https://drafts.csswg.org/scroll-animations-1/#scroll-notation">
<link rel="help" href="https://drafts.csswg.org/css-animations-2/#animation-timeline">
<meta name="assert" content="CSS animation correctly updates values when using the default scroll() timeline">
<link rel="match" href="scroll-timeline-default-ref.html">

<style>
  @keyframes update {
    from { transform: translateY(0px); }
    to { transform: translateY(200px); }
  }

  html {
    min-height: 100%;
    padding-bottom: 100px;
  }

  #box {
    width: 100px;
    height: 100px;
    background-color: green;
    animation: update 1s linear;
    animation-timeline: scroll();
  }

  #covered {
    width: 100px;
    height: 100px;
    background-color: red;
  }

  * {
    margin-top: 0px;
    margin-bottom: 0px;
  }
</style>

<div id="box"></div>
<div id="covered"></div>

<script src="/web-animations/testcommon.js"></script>
<script>
  document.documentElement.addEventListener('TestRendered', async () => {
    runTest();
  }, { once: true });

  async function runTest() {
    const scroller = document.scrollingElement;

    await waitForCompositorReady();

    // Move the scroller to the halfway point.
    const maxScroll = scroller.scrollHeight - scroller.clientHeight;
    scroller.scrollTop = 0.5 * maxScroll;

    await waitForNextFrame();
    await waitForNextFrame();

    document.documentElement.classList.remove("reftest-wait");
  }
</script>