RSpec controller test using cookies

preferences_controller.rb

class PreferencesController < ApplicationController

  def update
    @subdomain = cookies[:subdomain_name]
    @preference = Preference.find_by_subdomain_name(@subdomain)
    if @preference.update_attributes(params[:preference])
      flash[:success] = "Preferences for #{params[:preference][:subdomain_name]} updated."
      redirect_to spaces_path
    else
      @token = session[:token]
      render :edit
    end
  end

end

preferences_controller_spec.rb

describe PreferencesController do

  describe "when logged in" do
    before(:each) do
      # Not shown: variables that don't appear in the relevant tests
      @request.cookies[:subdomain_name] = "my_subdomain"  # This line is crucial!
      # The line that didn't work was as below:
      # cookies[:subdomain_name] = "my_subdomain"
    end

    describe "actions on existing preferences" do
      before(:each) do
        # As a bonus, I can set the subdomain_name with the cookie here
        @prefs = Preference.create!( subdomain_name: cookies[:subdomain_name], 
                                     access_token_string: session[:token],
                                     expire_after_days: 30 )
        @new_prefs = { :subdomain_name => cookies[:subdomain_name], 
                       :access_token_string => session[:token], 
                       :expire_after_days => 20 }
      end

      describe "PUT update" do
        # But here's where the cookie is required, because
        # the update method uses the cookie to find the record
        it "should update the days to expiration" do
          put :update, :id => @prefs, :preference => @new_prefs
          @prefs.reload
          @prefs.expire_after_days.should == @new_prefs[:expire_after_days].to_i
        end

        it "should redirect to the spaces page" do
          put :update, :id => @prefs, :preference => @new_prefs
          response.should redirect_to spaces_path
        end
      end
    end
  end

end