version_fail.rb

require 'rubygems'
require 'dm-core'
require 'dm-is-versioned'
require 'dm-timestamps'

DataMapper.setup(:default, 'mysql://localhost/my_db')
class Article
  include DataMapper::Resource

  property :id,               Integer, :serial => true
  property :title,            String
  property :updated_at,       DateTime

  is :versioned, :on => :updated_at
end

Article.auto_migrate!

article = Article.create(:title => "Test")

article.title = "Test 2"
article.save