animation-worklet/multiple-effects-on-same-target-driven-by-individual-local-time.https.html

<!DOCTYPE html>
<title>Multiple effects on same target driven by individual local time</title>
<link rel="help" href="https://drafts.css-houdini.org/css-animationworklet/">

<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/web-animations/testcommon.js"></script>
<script src="common.js"></script>

<style>
  #target {
    width: 100px;
    height: 100px;
    background-color: green;
  }
  #target2 {
    width: 100px;
    height: 100px;
    background-color: blue;
    box-shadow: 4px 4px 25px blue;
  }
</style>

<div id="target"></div>

<script id="simple_animate" type="text/worklet">
  registerAnimator("test_animator", class {
    animate(currentTime, effect) {
      let effects = effect.getChildren();
      effects[0].localTime = 0;
      effects[1].localTime = 1000;
    }
  });
</script>

<script>
  promise_test(async t => {
    await runInAnimationWorklet(document.getElementById('simple_animate').textContent);

    const effect = new KeyframeEffect(
        document.getElementById("target"),
        [
          { background: 'green' },
          { background: 'blue' },
        ],
        { duration: 2000 }
    );
    const effect2 = new KeyframeEffect(
        document.getElementById("target"),
        [
          { width: '100px' },
          { width: '200px' }
        ],
        { duration: 2000 }
    );

    const animation = new WorkletAnimation('test_animator', [effect, effect2]);
    animation.play();
    await waitForAsyncAnimationFrames(1);

    assert_equals(getComputedStyle(document.getElementById('target')).backgroundColor, "rgb(0, 128, 0)");
    assert_equals(getComputedStyle(document.getElementById('target')).width, "150px");
  }, `Animating multiple effects on the same target using effect specific local time should output values
  relative to each effects unique local time`);
</script>