chromium/third_party/blink/web_tests/external/wpt/infrastructure/assumptions/allowed-to-play.html

<!doctype html>
<title>&lt;audio and &lt;video> autoplay</title>
<link rel="help" href="https://html.spec.whatwg.org/multipage/media.html#dom-media-play">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/common/media.js"></script>
<video></video>
<script>
async_test(t => {
  const a = new Audio(getAudioURI("/media/sound_5"));
  a.play();
  assert_false(a.paused);
  a.onplaying = t.step_func_done();
}, "<audio> autoplay");

async_test(t => {
  const v = document.querySelector("video");
  v.src = getVideoURI("/media/movie_5");
  v.play();
  assert_false(v.paused);
  v.onplaying = t.step_func_done();
}, "<video> autoplay");
</script>