helper.rb

require 'digest/sha2'

module GoogleAuthoriseHelper
  def google_auth_url(user_id)
    encoded_id = encode_id_and_store(user.id)

  end

  def encode_id_and_store(user_id)
    sha256 = Digest::SHA2.new(256)
    sha256.digest(user_id)
    User.find(user_id).update(:google_callback_encoded_id => user_id)
  end
end

helper_spec.rb

require 'spec_helper'

describe GoogleAuthoriseHelper do
  include GoogleAuthoriseHelper
  describe "#google_auth_url" do
    #stub_chain(:current_user, :id).and_return 1
    google_auth_url(1).should eql ""
  end

  describe "encode_id_and_store" do
    encode_id_and_store(1).should eql ""
  end
end