beforeunload-sticky-activation-iframe.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>Beforeunload must be gated behind sticky activation: nested browsing context</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<p>If you happen to be running this test as a human, then be sure not to interact with any part of the page; that would invalidate the results!

<script>
setup({ single_test: true });

const iframe = document.createElement('iframe');
iframe.src = 'support/beforeunload-sticky-start.html';

window.onmessage = e => {
  assert_equals(e.data, 'navigated successfully');

  const desiredURL = (new URL('support/beforeunload-sticky-destination.html', location.href)).href;
  assert_equals(iframe.contentWindow.location.href, desiredURL);

  done();
};

document.body.append(iframe);
</script>

chromium/third_party/blink/web_tests/external/wpt/html/browsers/browsing-the-web/unloading-documents/beforeunload-sticky-activation-iframe.html