title: How do i test if the response was already set/send?
body: <p>I have the case that a express controller action "may" send contents. </p>
  
  <p>"Send" means either content was send (http 200) or the http status was set to something (http status 204 or a redirect for example)</p>
  
  <p>If nothing was sent/set a default routine should send a default content. </p>
  
  <p>how can i test in my default routine if the express controller action already set contents or set the status code ?</p>