Problem testing controller

Hello, I'm very new with Ruby (and Rails), but I need to make a test with testcase. I made an application that use openid login (following Ryan Bates's tutorial), where the session controller code is:

def create   if using_open_id?     open_id_authentication(params[:openid_url])   ...   end end

protected def open_id_authentication(openid_url)   authenticate_with_open_id(...) do |result, identity_url, registration|     if result.successful?     ...     end   end end

I tried to create a stub with no luck (maybe I don't really know how it works). I'd like to test the 'authenticate_with_open_id' block, currently I'm using simplecov to check the coverage and stops in that line.

Thanks