title: RSpec stub helper method in controller spec
body: <p>Found similar questions but surprisingly none, that I've found, give a simple answer...</p>
  
  <p>Trying to stub a helper method in my controller spec; not quite sure what object would need to be doubled?</p>
  
  <p>Controller calls this method:</p>
  
  <pre><code>#app/helpers/sessions_helper.rb
  
  def signed_in?
    current_user.present?
  end
  </code></pre>
  
  <p>I'd like to stub it in spec to return true/false.</p>