spec/fixtures/api/new-window-webview.html

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title></title>
  </head>
  <body>
    <script type="text/javascript">
      const code = `
var webview = document.createElement('webview')
webview.src = 'about:blank'
webview.addEventListener('did-finish-load', () => {
  ipcRenderer.send('webview-loaded')
}, {once: true})
document.body.appendChild(webview)
`
      open('about:blank').eval(code)
    </script>
  </body>
</html>