html/webappapis/animation-frames/callback-handle.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>AnimationTiming Test: FrameRequestCallback - valid callback handle</title>
<link rel="author" title="Intel" href="http://www.intel.com">
<link rel="help" href="https://html.spec.whatwg.org/multipage/#animation-frames">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<div id="log"></div>
<script>

  test(() => {
    let requestId = window.requestAnimationFrame(() => {});
    assert_greater_than(requestId, 0, "callback handle is a integer greater than zero");
  }, "Check window.requestAnimationFrame can return a valid callback handle");

</script>