test.rb

module MyModule
  def self.included(base)
    base.extend ClassMethods
    
    puts base.state_machine_class # Raises NotImplementedError
  end

  module ClassMethods
    def state_machine_class
      raise NotImplementedError
    end
  end
end

class MyModel
  include MyModule
  
  def self.state_machine_class
    StateMachineClass
  end
end