<!doctype html>
<link rel="author" href="mailto:emilio@crisal.io" title="Emilio Cobos Álvarez">
<link rel="author" href="mailto:https://mozilla.org" title="Mozilla">
<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1605610">
<link rel="help" href="https://drafts.csswg.org/web-animations/#extensions-to-the-element-interface">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script>
let t = async_test("animations started before initial-containing-block creation properly function");
let loaded = false;
let finished = false;
let span;

function check() {
  if (!loaded || !finished)
    return;

  assert_equals(getComputedStyle(span).opacity, "1", "Animation should be properly finished");
  t.done();
}

document.addEventListener("DOMContentLoaded", function() {
  span = document.createElement("span");
  span.id = "myspan";
  span.innerHTML = `Some content`;
  document.body.appendChild(span);

  let anim = span.animate([
    {
      opacity: "0",
    },
    {
      opacity: "1",
    },
  ], {
    duration: 300,
  });

  anim.finished.then(t.step_func(function() {
    finished = true;
    check();
  }));
});

window.addEventListener("load", t.step_func(function() {
  loaded = true;
  check();
}));
</script>
<!-- It is important that there are no more script after this stylesheet -->
<link rel="stylesheet" href="empty-sheet.css?pipe=trickle(d2)">
<body>
</body>
