Can't create a controller test

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 B.'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