rails route error when include module in controller

Question

when I include module in controller, the routing is not work, report 404 not found error, below is my code, very sample

ruby: 2.0, rails: 4.2.3

routes.rb

match ':controller(/:action(/:id))', via: :all

common.rb

module Common
  class A; end
end

test_controller.rb

class TestController < ApplicationController
  include Common  # when I delete this line , this route '/test/hello' works as expected,
                  # otherwise rails reports 404 not found

  def hello
    render :json => {msg: 'hello'}
  end
end

Answer 1

module/class name should start with capital letter Common

module Common
  class A; end
end