title: What are valid values for rspec :type?
body: <p>In an <code>rspec</code> test, it is possible to specify the type of the test e.g.</p>
  
  <pre><code>it 'should behave', type: :system do
     ...
  end
  </code></pre>
  
  <p>What are the valid values of :type, if so, where is it documented.</p>