chromium/third_party/blink/web_tests/external/wpt/html/semantics/embedded-content/media-elements/loading-the-media-resource/resource-selection-remove-src.html

<!doctype html>
<title>invoking resource selection by setting src; await stable state</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<div id=log></div>
<script>
var v;
var t = async_test(function(t) {
  v = document.createElement('video');
  v.onloadstart = t.step_func(function() { assert_unreached(); });
  v.setAttribute('src', ''); // runs resource selection algorithm, but it will wait running the sync section until this script has finished
  assert_equals(v.networkState, v.NETWORK_NO_SOURCE);
  v.removeAttribute('src'); // will make resource selection algorithm revert to NETWORK_EMPTY and abort (in the sync section)
  assert_equals(v.networkState, v.NETWORK_NO_SOURCE);
  window.onload = t.step_func(function() { t.done(); });
});
</script>
<script>
t.step(function() {
  assert_equals(v.networkState, v.NETWORK_EMPTY);
});
</script>