css/css-backgrounds/animations/invalidation/background-color-transition-with-delay.html

<!DOCTYPE html>
<html class="reftest-wait">
<link rel="help" href="https://drafts.csswg.org/css-backgrounds-3/#background-color">
<link rel="match" href="background-color-transition-with-delay-ref.html">
<style>
.container {
  width: 100px;
  height: 100px;
  background-color: rgb(0, 200, 0);
  transition: background-color 200000ms steps(2) -99999.9ms;
}
</style>
<script src="/common/reftest-wait.js"></script>
<body>
<div class="container" id="target"></div>

<script>
// This test differs from "background-color-transition.html" because it runs the
// transition starting from the set background color, rather than using a
// delay to start in the middle of the transition. This tests a new codepath
// where the first frame of the transition has the original background color,
// which is why we need the transition fully running. Since we are using the
// step(2) in the animation, so it is enough to wait for two frames and the
// animation should be in its mid-point, that's the time we should take
// screenshot.
function startTransition() {
  requestAnimationFrame(() => {
    document.getElementById('target').style.backgroundColor = "rgb(200, 0, 0)";
    document.getAnimations()[0].ready.then(() => {
      requestAnimationFrame(() => {
        requestAnimationFrame(() => {
          takeScreenshot();
        });
      });
    });
  });
}

requestAnimationFrame(startTransition);
</script>
</body>
</html>