css/css-view-transitions/web-animations-api.html

<!DOCTYPE html>
<html class=reftest-wait>
<title>View transitions: capture opacity elements</title>
<link rel="help" href="https://drafts.csswg.org/css-view-transitions-1/">
<link rel="author" href="mailto:khushalsagar@chromium.org">
<link rel="match" href="web-animations-api-ref.html">
<meta name="fuzzy" content="maxDifference=0-2; totalPixels=0-500">

<script src="/common/reftest-wait.js"></script>
<style>
#first {
  background: blue;
  width: 100px;
  height: 100px;
  contain:  paint;
}
#second {
  background: green;
  width: 100px;
  height: 100px;
  contain: paint;
}

/* Unset all animations since the test drives it using WA-API */
html::view-transition-group(*),
html::view-transition-image-pair(*),
html::view-transition-new(*),
html::view-transition-old(*) {
  animation: unset;
}

html::view-transition-group(root){
  opacity: 0;
}

</style>
<div id=first></div>
<div id=second></div>
<script>
failIfNot(document.startViewTransition, "Missing document.startViewTransition");

function setAnimation() {
  document.documentElement.animate({ transform: ['translate(100px)', 'translate(100px)'] }, { duration: 10000, pseudoElement: '::view-transition-group(first)'});
  document.documentElement.animate({ transform: ['translate(150px)', 'translate(150px)'] }, { duration: 10000, pseudoElement: '::view-transition-group(second)'});
  requestAnimationFrame(takeScreenshot);
}

async function runTest() {
  first.style.viewTransitionName = "first";
  document.startViewTransition(() => {
    first.style.viewTransitionName = "";
    second.style.viewTransitionName = "second";
    requestAnimationFrame(setAnimation);
  });
}
onload = () => requestAnimationFrame(() => requestAnimationFrame(runTest));
</script>