unit testing - how do you stub a local variable in an rspec controller test -

i've implemented omniauth (using ryan bates' screencast http://asciicasts.com/episodes/235-omniauth-part-1) , writing rspec tests functionality , have ran trouble testing authentifications#create action. i'm @ quite loss how test 1 -- in particular how stub local variable omniauth. no matter try keep can't tests work.

taking cut down version of action, how test new called on user example

 #cut down version of authentifications controller code attempting test    def create     omniauth = request.env["omniauth.auth"]     authentification = authentification.find_by_provider_and_uid(omniauth['provider'], omniauth['uid'])          ....     user = user.new     ....   end    #example test      "should create new user"                   subject.stub_chain(:request,:env) {{"omniauth.auth" => {'provider' =>1, 'uid' => 2}}}         user.should_receive(:new)         post :create       end 

i did :

class sessionscontroller < applicationcontroller    def create      @user = user.find_by_auth_hash(auth_hash)    end     def auth_hash      request.env['omniauth.auth']    end  end   describe sessionscontroller    'should allow login'      controller.stub!(:auth_hash).and_return({'provider' => 'twitter', 'uid' => '1234'})      :create, :provider => 'twitter'      assigns(:user).should_not be_nil    end  end  

hope helps.