css/css-view-transitions/to-keyframe-values.html

<!DOCTYPE html>
<title>CSS View Transitions: Verify to keyframe values</title>
<link rel="help" href="https://drafts.csswg.org/css-view-transitions-1/">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
:root { view-transition-name: none }
#item {
  view-transition-name: item;
  width: 10px;
  height: 10px;
  position: relative;
}
.shifted {
  left: 20px;
}
::view-transition-group(*) {
  animation-play-state: paused;
}
</style>
<div id=item></div>

<script>
async_test((t) => {
  document.startViewTransition(() => item.classList.add("shifted")).ready.then(() => {
    let anims = document.getAnimations().filter(a => {
      return a.effect.pseudoElement == '::view-transition-group(item)';
    });

    t.step(() => {
      assert_equals(anims.length, 1);
      assert_equals(anims[0].effect.getKeyframes().length, 2);
      assert_true(anims[0].effect.getKeyframes()[0].transform.startsWith("matrix"),
        `keyframe[0] should be matrix, not ${anims[0].effect.getKeyframes()[0].transform}`);
      assert_true(anims[0].effect.getKeyframes()[1].transform.startsWith("matrix"),
        `keyframe[1] should be matrix, not ${anims[0].effect.getKeyframes()[1].transform}`);
    });
    t.done();
  });
});
</script>