current_spec.rb

# spec/controllers/admin/restaurant_offers_controller.spec.rb
describe "GET :edit" do
      before do
        @restaurant_offer.stub(:editable?).and_return true
      end

      def doittoit
        get :edit, id: @restaurant_offer.id, restaurant_id: @resto.id
      end

      it "is successful" do
        doittoit
        response.should be_successful
      end

      it "renders the :edit template" do
        doittoit
        response.should render_template('edit')
      end

    end

refactored_spec.rb

describe "GET :edit" do
      let(:get_edit) do
         get :edit, id: @restaurant_offer.id, restaurant_id: @resto.id
      end

      before do
        @restaurant_offer.stub(:editable?).and_return true
      end

      before(:each) do
        get_edit
      end

      it "is successful" do
        response.should be_successful
      end

      it "renders the :edit template" do
        response.should render_template('edit')
      end

end