css/css-animations/dialog-animation.html

<!doctype html>
<meta charset=utf-8>
<title>CSS Animations on a &lt;dialog></title>
<link rel="help" href="https://drafts.csswg.org/css-animations-1/">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="support/testcommon.js"></script>
<style>

dialog[open] {
    animation: dialog-open-animation 1ms;
}

@keyframes dialog-open-animation {
    from { opacity: 0 }
}

</style>
<div id="log"></div>
<script>

"use strict";

promise_test(async t => {
  const dialog = addElement(t, "dialog");

  // Open the dialog a first time, this should trigger a CSS Animation.
  dialog.open = true;
  const animations = dialog.getAnimations();
  assert_equals(animations.length, 1, "As the <dialog> is shown intially an animation is started");

  await animations[0].finished;

  await waitForNextFrame();

  dialog.open = false;
  assert_equals(dialog.getAnimations().length, 0, "As the <dialog> is closed the animation is removed");

  await waitForNextFrame();

  dialog.open = true;
  assert_equals(dialog.getAnimations().length, 1, "As the <dialog> is shown again an animation is started again");
}, "CSS Animations tied to <dialog open> are canceled and restarted as the dialog is hidden and shown");
</script>