test.rb

module StateMachineConcern
  extend ActiveSupport::Concern

  included do |base|
    state_machine_class.states.each do |state|
      # do something with each state
    end
  end

  class_methods do
    def transition_class
      raise NotImplementedError
    end

    def state_machine_class
      raise NotImplementedError
    end

    def initial_state
      state_machine_class.initial_state
    end
  end
end

class MyModel < ActiveRecord::Base
  def self.transition_class
    MyModelTransitionClass
  end

  def self.state_machine_class
    MyModelStateMachineClass
  end
end