Routing to delete in my restful web service is not working

I am having an problem routing to my delete method on my restful web service for permissions. My routes are set up as follows :

  namespace :service do
      namespace :v1 do
        resources :surveys do
          resources :permissions, only: [:index, :create, :delete, :update]
        end
      end
    end

The following spec passes

   it "routes toya expected controller method" do
      {:get => 'service/v1/surveys/3/permissions'}.should route_to(controller: 'service/v1/permissions', action: 'index', :survey_id => "3")
   end

This spec fails

describe 'DELETE :destroy' do
    it "routes to expected controller method" do
      {:delete => 'service/v1/surveys/3/permissions'}.should route_to(controller: 'service/v1/permissions', action: 'destroy', :survey_id => "3")
    end
  end

The snippet from my controller is as follows

module Service
  module V1
    class PermissionsController < ApplicationController

      before_filter :authenticate_user!, :only => []

      def index
        render :json => permissions,  :each_serializer => Service::V1::PermissionSerializer
      end

 def destroy
            debugger
            # cant route to here 
            a = 1
      end

    end
  end
end

Any suggestions ? I am slightly confused between destroy and delete, I think that might be the source of my problem