title: Is there a way to test which layout an Action Mailer email is rendered with?
body: <p>I have some Action Mailer email messages and I would like to test which layout will be used to render the email. I found <a href="http://ryanbriones.com/blog/nerd/2008/10/23/testing-actionmailer-renders-template.html" rel="noreferrer">this example on the web</a>, but it's from 2008 and doesn't work with Rails 3.2 and presumably later versions.</p>
  
  <p>My motivation for this is that I'd like to write a unit test that asserts that the mailer was rendered with a particular layout so if that is changed, the test will break.</p>