css/css-color/body-opacity-0-to-1-stacking-context.html

<!doctype html>
<html class="reftest-wait">
<link rel="help" href="https://drafts.csswg.org/css-color-3/#transparency">
<link rel="match" href="greensquare-ref.html">
<script src="/common/reftest-wait.js"></script>
<script src="/common/rendering-utils.js"></script>
<body style="opacity: 0">
  <p>Test passes if you see a green square, and no red.</p>
  <div style="position: absolute; background: red">
    <div style="will-change: opacity; width: 12em; height: 12em; background: green"></div>
  </div>
</body>
<script>
  waitForAtLeastOneFrame().then(() => {
    document.body.style.opacity = 1;
    takeScreenshot();
  });
</script>