gistfile1.rb

# Trying to replicate http://datamapper.lighthouseapp.com/projects/20609-datamapper/tickets/470-memcaching-can-t-marshal-dm-objects#ticket-470-19
require 'rubygems'
require 'dm-core'
require 'dm-migrations'
require 'dm-timestamps'

DataMapper::Logger.new($stdout, :debug)
DataMapper.setup(:default, 'postgres://localhost/test') # createdb test

class TestDm
  include DataMapper::Resource

  property :id, Serial
  property :created_at, DateTime 
  property :created_on, Date 
  property :updated_at, DateTime
  property :updated_on, Date

  has n, :tests, :through => :testing 
  has n, :testing
end

class Testing
  include DataMapper::Resource
   belongs_to :test_dm, :key => true
   belongs_to :test, :key => true
end
class Test
  include DataMapper::Resource
  property :id, Serial
  has n, :testing
end

DataMapper.finalize
DataMapper.auto_migrate!
test = Test.create.tap do |t|
  t.testing.create(:test => Test.create)
end
puts Marshal.load(Marshal.dump(test)).inspect