title: How do I test a devise parameter sanitizer
body: <p>I've implemented the code below so I can update user attributes via strong parameters. It's straight out of devise's documentation and I understand it pretty well.</p>
  
  <p>The problem however is that I'm really new to testing. I'm using SimpleCov and it tells me the <code>u.permit</code> bit is not covered. Unfortunately, I'm not quite sure how to test for this.</p>
  
  <p>I'm using rspec and I'd like to know if anyone could point me in the right direction.</p>
  
  <p>How do I test for this?</p>
  
  <pre><code>devise_parameter_sanitizer.for(:account_update) do |u|
    u.permit(:username, :email, :password, :password_confirmation)
  end
  </code></pre>