rails/activerecord/test/models/vegetables.rb

class Vegetable < ActiveRecord::Base
  validates_presence_of :name

  def self.inheritance_column
    "custom_type"
  end
end

class Cucumber < Vegetable
end

class Cabbage < Vegetable
end

class GreenCabbage < Cabbage
end

class KingCole < GreenCabbage
end

class RedCabbage < Cabbage
  belongs_to :seller, class_name: "Company"
end