test.rb

module Uno
    def queue_mode
      @queue_mode ||= :single
    end

    def queue_mode=(value)
      @queue_mode = value
    end

    def enqueue_mode(mode)
      @queue_mode = mode
    end
end

class Dos
  extend Uno
end

class Tres < Dos
  enqueue_mode :enqueue_all

  def self.perform
    puts @queue_mode
    true
  end
end

class Cuatro < Dos
  def self.perform
    puts @queue_mode
  end
end

puts 'uno'
puts Dos.queue_mode
puts Tres.perform
puts Cuatro.queue_mode