remote-playback/watch-availability-initial-callback.html

<!DOCTYPE html>
<html>
  <title>
    Test that the callback is called after the Promise returned by watchAvailability() resolves
  </title>
  <script src="/resources/testharness.js"></script>
  <script src="/resources/testharnessreport.js"></script>
  <script src="/common/media.js"></script>
  <script>
    async_test(t => {
      let v = document.createElement("video");
      v.src = getVideoURI("/media/movie_5");

      let promiseResolved = false;

      v.remote
        .watchAvailability(t.step_func_done(() => assert_true(promiseResolved)))
        .then(
          t.step_func(() => {
            promiseResolved = true;
          }),
          t.unreached_func()
        );
    }, "Test that the callback is called after the Promise returned by watchAvailability() resolves.");
  </script>
</html>