mozilla-release/testing/web-platform/tests/fullscreen/api/element-request-fullscreen-dialog-manual.html

<!DOCTYPE html>
<title>Element#requestFullscreen() for dialog element</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="../trusted-click.js"></script>
<div id="log"></div>
<dialog></dialog>
<script>
async_test(t => {
  var dialog = document.querySelector("dialog");
  assert_true(dialog instanceof HTMLDialogElement);
  trusted_request(t, dialog);
  document.onfullscreenchange = t.unreached_func("fullscreenchange event");
  document.onfullscreenerror = t.step_func_done();
});
</script>