require 'mongoid'
#=> false
class Foo
  include Mongoid::Document
  field :name, type: String
  validates :name, uniqueness: true
end
#=> {:uniqueness=>true}
 
class Bar < Foo
end
#=> nil
 
Foo.create!(name: "server1")
#=> #<Foo _id: 51109c8d5427dbe7e2000001, _type: nil, name: "server1">
bar = Bar.new(name: "server1")
#=> #<Bar _id: 51109c8d5427dbe7e2000002, _type: "Bar", name: "server1">
bar.valid?
#=> true