<!DOCTYPE html>
<body>
  <script src=/resources/testharness.js></script>
  <script src=/resources/testharnessreport.js></script>
  <iframe allow="document-access 'none'" src="resources/child.html"></iframe>
  <script>
    async_test(function (t) {
      // Ensure post message works correctly.
      window.onmessage = t.step_func((e) => {
        if (e.data == 'load') {
          frames[0].postMessage('ping');
        } else if (e.data == 'pong') {
          t.done();
        }
      });
      try {
        // Test that the parent is not allowed to access the child either.
        frames[0].alert;
        assert_unreachable('Security Error should have been thrown');
      } catch(e) {
        assert_equals(e.name, 'SecurityError', 'Security Error thrown');
      }
    });
  </script>
</body>