<!DOCTYPE html>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<body>
<script>
promise_test(async t => {
  assert_implements("HTMLPortalElement" in self);
  let portal = document.createElement('portal');
  portal.src = "resources/portal-close-window.html";
  let waitForMessage = new Promise((resolve, reject) => {
    portal.onmessage = e => resolve(e.data);
    document.body.appendChild(portal);
  });
  document.body.appendChild(portal);
  var message = await waitForMessage;
  assert_equals(message, false);
  t.add_cleanup(() => { document.body.removeChild(portal); });
}, "A portal's window cannot be closed");
</script>
</body>