Can't get this Rspec test to pass

Hello,
I'm completely new to Rspec testing and I'm finding it very difficult to mock specific objects.

In this test, I have a before block setup as such:

Code:
  before do
    setup_controller_for_warden
    controller.session[:operation_id] = 1
    @operator = Factory :operator
    sign_in :operator, @operator
            
    @persist_herd = Herd.new
    @persist_herd.operation_id = 1;
    @persist_herd.herd_name = 'Persisted Herd (herd_rations_controller_spec)'
    @persist_herd.save!
  end

  describe "GET new" do
    it "assigns a new herd_ration as @herd_ration" do
      HerdRation.stub(:new){ mock_herd_ration }
      Herd.stub(:find).with(1) { @persistant_herd }
      
      get :new, :herd_id => 1
      assigns(:herd_ration).should be(mock_herd_ration)
      response.should be_success
    end
  end


and here's my controller method:

  def new
    @herd_ration = HerdRation.new
    @herd = Herd.find(params[:herd_id])
    
    if @herd
      respond_with(@herd_rations, :layout=> !request.xhr?)
    else
      redirect_to(root_url, :notice => 'No herd selected for ration.')
    end
  end
Here's the catch - we have this groovy little plugin that globally enforces a model scope via a session id, in this case: session[peration_id].

Here's the code for the plugin:

Code:
module ApplicationScopeManager


   mattr_accessor :global_scope
   @@global_scope = []

   mattr_accessor :local_scope
   @@local_scope = {}

   def self.included(base)
      base.send :extend, ClassMethods
   end

   def self.setup
      yield self
   end

   module ClassMethods


      def method_missing(name, *args, &block)

         return acts_as_scope_manager($1, args) if name.to_s =~ /^acts_as_scope_manager_for_(.*)/
         
         return honors_scope_of($1, args) if name.to_s =~ /^honors_scope_of_(.*)/
         
         return current_scope_for($1) if name.to_s =~ /^current_scope_for_(.*)/
         
         super
      end

      def current_scope_for(scope)
         Thread.current[scope.to_sym]
      end

      def acts_as_scope_manager(scope, *args)
         options = args[0].extract_options! if args
         send :include, InstanceMethods

         set_global_scope(scope,options[:with_global_scope]) if options[:with_global_scope]

         send :before_filter, "set_scope_for_#{scope}".to_sym if self.ancestors.include? ActionController::Base
         send :default_scope, where(scope.to_sym => send("current_scope_for_#{scope}".to_sym)[:finder_scope]).create_with(scope.to_sym =>
         send("current_scope_for_#{scope}".to_sym)[:creator_scope]) if (self.ancestors.include? ActiveRecord::Base) && Thread.current[scope.to_sym]
      end

      alias honors_scope_of acts_as_scope_manager

      private


      def set_global_scope(scope, *args)
         Thread.current[scope.to_sym] = {:global_scope => args}
      end

   end

   module InstanceMethods

      def method_missing(name, *args, &block)

         return set_scope_for($1, args) if name.to_s =~ /^set_scope_for_(.*)/

         super
      end

      private

      def set_scope_for(scope, *args)
         if session[scope].class == Array
            application_scope = {:finder_scope => session[scope], :creator_scope => nil }
         else
            application_scope = {:finder_scope => [session[scope]], :creator_scope => session[scope] }
         end

         application_scope[:finder_scope] = application_scope[:finder_scope] + Thread.current[scope.to_sym][:global_scope] if Thread.current[scope.to_sym][:global_scope]

         Thread.current[scope.to_sym] = application_scope

      end

   end
end
This plugin enforces any model that calls the honors_scope_of_operation_id to include a lookup of the session[peration_id] in all database calls. For instance if I do a Model.find(params[:id]) it will automatically add a WHERE "field_name"."operation_id" = to the where clause. The problem I'm having is that I can't seem to mock the session[peration_id] in my Rspec tests. I thought setting it this way controller.session[peration_id] = 1 in the before block would have been sufficient.

Any ideas?