puppeteer/test/assets/main-frame.html

<!DOCTYPE html>
<script>
  window.addEventListener('DOMContentLoaded', () => {
    const iframe = document.createElement('iframe');
    const url = new URL(location.href);
    url.hostname = 'domain2.test';
    url.pathname = '/inner-frame1.html';
    iframe.src = url.toString();
    document.body.appendChild(iframe);
  }, false);
</script>