gistfile1.rb

#admin_routes_spec.rb

require "spec_helper"

describe "Admin Routes" do
  describe "GET '/admin'" do
  
    it "should block access if not on www" do
      { :get => "http://foo.example.com/admin" }.should_not be_routable 
    end

    it "should allow access if on www" do
      { :get => "http://www.example.com/admin" }.should route_to(:controller => "admin/dashboards", :action => "show")
    end
  end
end

# routes.rb (excerpt)

namespace :admin do
  constraints(RootDomain) do
    resource :dashboard, :only => :show
    root :to => "dashboards#show"
  end
end

# app/lib/root_domain.rb

class RootDomain
  def self.matches?(request)
    request.subdomain.blank? || request.subdomain == "www"
  end
end