title: How to test ActionMailer delivery_method in RSpec?
body: <p>I have 2 <code>delivery_method</code>s, switchable using a environment variable like so:</p>
  
  <pre><code>config.action_mailer.delivery_method = :mailjet
  </code></pre>
  
  <p>OR</p>
  
  <pre><code>config.action_mailer.delivery_method = :smtp
  </code></pre>
  
  <p>How do test the <code>delivery_method</code> in RSpec tests?</p>