title: Fast Testing: How to test Mailer without Loading Rails
body: <p>I've got some work to do refactoring a mailer class.  I don't want to spend all my time loading rails and waiting to see if tests are passing.  I'd like to just not include spec_helper and speed up my tests.</p>
  
  <p>How do I just include ActionMailer? </p>
  
  <p>I tried this:</p>
  
  <pre><code>require 'action_mailer'
  </code></pre>
  
  <p>but I stil end up with this error:</p>
  
  <pre><code>uninitialized constant ActionMailer (NameError)
  </code></pre>
  
  <p>Any ideas?</p>