Datamapper DataMapper → 0.10.0

Another spec courtesy of the prolific mrship:

require 'rubygems'
  
USE_DM_0_9 = false
 
if USE_DM_0_9
  DM_GEMS_VERSION   = "0.9.11"
  DO_GEMS_VERSION   = "0.9.12"
else
  DM_GEMS_VERSION   = "0.10.0"
  DO_GEMS_VERSION   = "0.10.0"
end
 
gem "data_objects",   DO_GEMS_VERSION
# gem "do_postgres",    DO_GEMS_VERSION # If using another database, replace this
gem "do_sqlite3",     DO_GEMS_VERSION # If using another database, replace this
gem "dm-core",        DM_GEMS_VERSION         
gem "dm-aggregates",  DM_GEMS_VERSION   
gem "dm-migrations",  DM_GEMS_VERSION   
gem "dm-timestamps",  DM_GEMS_VERSION   
gem "dm-types",       DM_GEMS_VERSION        
gem "dm-validations", DM_GEMS_VERSION  
gem "dm-serializer",  DM_GEMS_VERSION  

require "data_objects"
require "dm-core"
require "dm-aggregates"
require "dm-migrations"
require "dm-timestamps"
require "dm-types"
require "dm-validations"
require "dm-serializer"

require 'spec'
 
SQLITE_FILE = File.join(`pwd`.chomp, "test.db")
 
DataMapper.setup(:default, "sqlite3:#{SQLITE_FILE}")
DataMapper.setup(:reloaded, "sqlite3:#{SQLITE_FILE}")
 
class Farm
  include DataMapper::Resource

  property :id, Serial
  
  has n, :cows, :order => [:cow_id]
end
 
class Cow
  include DataMapper::Resource

  property :id, Serial
  property :cow_id, Integer
  property :name, String

  # Comment out the following line to make the spec pass
  validates_is_unique :name, :scope => [:farm]
  
  belongs_to :farm
end
 
module IdentityMapHelper
  def reload(object)
    object.class.get(object.id)
  end
  
  def with_db_reconnect(&blk)
    original_repository = DataMapper::Repository.context.pop
    repository(:reloaded, &blk)
    DataMapper::Repository.context << original_repository
  end
end
 
Spec::Runner.configure do |config|
  include IdentityMapHelper
  
  config.before(:each) do
    Farm.auto_migrate!
    Cow.auto_migrate!
  end
  
  config.before(:each) do    
    DataMapper::Repository.context << repository(:default)
  end
  
  config.after(:each) do
    DataMapper::Repository.context.pop
  end
end
 
describe "Swapping elements in a collection using #[] accessor" do
  before(:each) do
    @bluebell_farm = Farm.new
    @cow_1 = Cow.new(:cow_id => 1, :name => "Daisy")
    @cow_2 = Cow.new(:cow_id => 2, :name => "Florence")
    @cow_4 = Cow.new(:cow_id => 3, :name => "Juicysteak")
    @cow_3 = Cow.new(:cow_id => 4, :name => "Tastyburger")
    
    @bluebell_farm.cows << @cow_1 << @cow_2 << @cow_3 << @cow_4
  end
  
  it "should let you swap elements and not lose the association" do
    @bluebell_farm.cows[0].farm.should_not be_nil
    @bluebell_farm.cows[1].farm.should_not be_nil
    @bluebell_farm.cows[0], @bluebell_farm.cows[1] = @bluebell_farm.cows[1], @bluebell_farm.cows[0]
    @bluebell_farm.cows[0].farm.should_not be_nil
    @bluebell_farm.cows[1].farm.should_not be_nil
  end
  
  it "should let you swap elements and not lose the association without having to save" do
    @bluebell_farm.cows[0].farm.should_not be_nil
    @bluebell_farm.cows[1].farm.should_not be_nil
    @bluebell_farm.cows[0], @bluebell_farm.cows[1] = @bluebell_farm.cows[1], @bluebell_farm.cows[0]
    @bluebell_farm.save
    @bluebell_farm.cows[0].farm.should_not be_nil
    @bluebell_farm.cows[1].farm.should_not be_nil
  end
end

I have not given any thought to why the first example fails (after the switch), but it looks clearly wrong to me. Any thoughts?