mozilla-release/testing/web-platform/tests/fullscreen/api/element-request-fullscreen-and-remove-iframe-manual.html

<!DOCTYPE html>
<title>Element#requestFullscreen() in iframe followed by removing the iframe</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="../trusted-click.js"></script>
<div id="log"></div>
<iframe allowfullscreen></iframe>
<script>
async_test(t => {
  const iframe = document.querySelector("iframe");
  const iframeDocument = iframe.contentDocument;

  document.onfullscreenchange = t.unreached_func("fullscreenchange event");
  document.onfullscreenerror = t.unreached_func("fullscreenerror event");
  iframeDocument.onfullscreenchange = t.unreached_func("iframe fullscreenchange event");
  iframeDocument.onfullscreenerror = t.unreached_func("iframe fullscreenerror event");

  trusted_click(t, () => {
    iframeDocument.body.requestFullscreen();
    iframe.remove();
    // No events will be fired, end test after 100ms.
    step_timeout(t.step_func_done(() => {
      assert_equals(document.fullscreenElement, null);
      assert_equals(iframeDocument.fullscreenElement, null);
    }), 100);
  }, document.body);
});
</script>