Create Users in Factory Girl with OmniAuth?

I am currently creating an application that uses OmniAuth to create and authenticate users. I am experiencing problems during testing due to Factory Girl cannot generate users without OmniAuth.

I have several different ways to get a Factory girl to create users with omniauth, but none of them have been successful.

I added the following 2 lines to my spec_helper file

OmniAuth.config.test_mode = true \\ allows me to fake signins
OmniAuth.config.add_mock(:twitter, { :uid => '12345', :info => { :nickname => 'Joe Blow' }})

current factories .rb

FactoryGirl.define do
  factory :user do
    provider "twitter"
    sequence(:uid) { |n| "#{n}" }
    sequence(:name) { |n| "Person_#{n}" }
  end
end

The following test is currently failing as no user is created

let(:user) { FactoryGirl.create(:user) }
before { sign_in user }

describe "registering" do

  it "should increment" do
    expect do
      click_button 'register'
    end.to change(user.rounds, :count).by(1)
end

How do I change my factories / tests to get Factory Girl to create test users using OmniAuth?

Edit: I used the RailsCast manual to configure Omniauth ,

#create function inside user.rb
def self.create_with_omniauth(auth)
  create! do |user|
    user.provider = auth["provider"]
    user.uid = auth["uid"]
    user.name = auth["info"]["name"]
  end
end

,

#create inside the session_controller
def create
  auth = request.env["omniauth.auth"]
  user = User.find_by_provider_and_uid(auth["provider"], auth["uid"]) ||    User.create_with_omniauth(auth)
  session[:user_id] = user.id
  redirect_to root_url, :notice => "Signed in!"
end