Enumerates routed controllers and actions and checks if they exist in the code (simple and quick, without corner cases). Tested on Rails 3.2.8

quick_route_tester.rb

Rails.application.eager_load!
all_routes = Rails.application.routes.routes

controllers=ApplicationController.descendants
#controller_names = controllers.collect {|c| c.to_s.underscore.sub('_controller','') }
controller_names={}
controllers.each {|c|
  controller_names[c.to_s]=c.to_s.underscore.sub('_controller','')
}.size

missing_stuff_names = {}

all_routes.each {|route|
    routed_controller = route.defaults[:controller]
    routed_action = route.defaults[:action]
    next unless routed_controller
    #puts "routed_controller: #{routed_controller} , routed_action: #{routed_action}"
    unless controller_names.values.include? routed_controller
        #controller is routed but totally missing from code
        missing_stuff_names[routed_controller]||=[]
        missing_stuff_names[routed_controller] << routed_action
        pp "#{routed_controller} totally missing, should also have action: #{routed_action}"
      else
        unless controller_names.key(routed_controller).constantize.action_methods.to_a.include? routed_action
          #controller is present in code but misses some routed actions
          missing_stuff_names[routed_controller]||=[]
          missing_stuff_names[routed_controller] << routed_action
          pp "#{routed_controller} missing action: #{routed_action}"
        end
    end
    
}.size

pp missing_stuff_names