src/third_party/web_platform_tests/mediasession/playbackstate.html

<!DOCTYPE html>
<title>MediaSession.playbackState attribute</title>
<script src=/resources/testharness.js></script>
<script src="/resources/testharnessreport.js"></script>
<script>

test(function() {
  assert_equals(window.navigator.mediaSession.playbackState, "none");
}, 'Test that playbackState is initialized as "none"');

test(function() {
  var states = [ "paused", "playing", "none" ];
  for (let state of states) {
    window.navigator.mediaSession.playbackState = state;
    assert_equals(window.navigator.mediaSession.playbackState, state);
  }
}, 'Test that playbackState is read/write');

test(function() {
  var invalidStates = [ "invalid", "" ];
  for (let state of invalidStates) {
    window.navigator.mediaSession.playbackState = state;
    assert_equals(window.navigator.mediaSession.playbackState, "none");
  }
}, 'Test that warning is thrown when setting invalid playbackState');

</script>