wrong_liskov_substitution_example.rb

class Message
  attr_reader :status
  
  def initialize
    @status = :started
  end

  def cancel
    @status = :canceled
  end

  # ...
end

class UrgentMessage < Message
  attr_reader :status

  def cancel
      raise ForbiddenCancelError if @status == :started
      @status = :canceled
  end
  
end