xmlhttprequest-sync-block-scripts.html

<!doctype html>
<meta charset=utf-8>
<title>Check that while a sync XHR is in flight async script loads don't complete and run script</title>
<script src=/resources/testharness.js></script>
<script src=/resources/testharnessreport.js></script>
<body>
<script>
var scriptRan = false;
var onloadFired = false;
test(function() {
  var s = document.createElement("script");
  s.src = "data:application/javascript,scriptRan = true;";
  s.onload = function() { onloadFired = true; }
  document.body.appendChild(s);
  var xhr = new XMLHttpRequest();
  xhr.open("GET", "data:,", false);
  xhr.send();
  assert_false(scriptRan, "Script should not have run");
  assert_false(onloadFired, "load event for <script> should not have fired");
});
</script>
</body>

chromium/third_party/blink/web_tests/external/wpt/xhr/xmlhttprequest-sync-block-scripts.html