problem.rb

require 'mongoid'
require './lib/arnold'

class Test
  include Mongoid::Document
  
  field :name
  field :job
  field :rank
end

test = Test.new name: 'Arnold', job: 'Boss', rank: 1

test.edit # just :wq
=> #<Test _id: , _type: nil, name: "Arnold", job: "Boss", rank: 1>
# _id gets erased!