css/css-contain/content-visibility/content-visibility-009.html

<!doctype HTML>
<html class="reftest-wait">
<meta charset="utf8">
<title>CSS Content Visibility: hidden stops painting when added (positioned)</title>
<link rel="author" title="Vladimir Levin" href="mailto:vmpstr@chromium.org">
<link rel="help" href="https://drafts.csswg.org/css-contain/#content-visibility">
<link rel="match" href="positioned-container-ref.html">
<meta name="assert" content="content-visibility subtrees stop painting when hidden is added">

<script src="/common/reftest-wait.js"></script>

<style>
#container {
  width: 150px;
  height: 150px;
  background: lightblue;
}
.positioned {
  position: absolute;
  top: 0;
  left: 0;
}
.hidden {
  content-visibility: hidden;
}
#child {
  width: 50px;
  height: 50px;
  background: red;
}
</style>

<div id=container class=positioned>
  Test fails if you can see this text or a red box.
  <div id=child></div>
</div>

<script>
function runTest() {
  const container = document.getElementById("container");
  container.classList.add("hidden");
  requestAnimationFrame(takeScreenshot);
}

window.onload = runTest;
</script>
</html>