Mongoid failing many to many spec

gistfile1.rb

require 'spec_helper'

describe Mongoid::Relations::Referenced::ManyToMany do

  before(:all) do
    Mongoid.raise_not_found_error = true
  end

  before do
    [
      Person, Preference, Event, Tag,
      UserAccount, Agent, Account, Business, User,
      Artwork, Exhibition, Exhibitor
    ].map(&:delete_all)
  end

  let(:person) do
    Person.create
  end

  let(:preference) do
    Preference.new(:name => 'foo', :value => 'bar')
  end

  describe "#<<" do

    it "appends a new document to the relation" do

      person.preferences.should == []

      person.preferences << Preference.new(:name => 'db', :value => 'mongo')

      person.preferences.size.should == 1
      person.preferences.map(&:name).should == ['foo']
    end
    
    it "appends the existing document to the relation" do

      person.preferences.should == []

      person.preferences << preference

      person.preferences.size.should == 1
      person.preferences.map(&:name).should == ['foo']
    end

    it "appends the document to the relation when ids are used" do

      person.preference_ids.should == []

      person.preference_ids << preference.id

      person.preference_ids.size.should == 1
      person.preference_ids.should == [preference.id]
      
    end
     
  end
  
end

Output running on mongoid master:

Failures:

1. Mongoid::Relations::Referenced::ManyToMany#<< appends a new document to the relation
   Failure/Error: person.preferences.size.should == 1
   expected: 1
   got: 0 (using ==)

   ./spec/functional/mongoid/relations/referenced/many_to_many_failing_spec.rb:33:in `block (3 levels) in <top (required)>'

2. Mongoid::Relations::Referenced::ManyToMany#<< appends the existing document to the relation
   Failure/Error: person.preferences.size.should == 1
   expected: 1
   got: 0 (using ==)

   ./spec/functional/mongoid/relations/referenced/many_to_many_failing_spec.rb:43:in `block (3 levels) in <top (required)>'

Finished in 0.15422 seconds
3 examples, 2 failures

Failed examples:

rspec ./spec/functional/mongoid/relations/referenced/many_to_many_failing_spec.rb:27 # Mongoid::Relations::Referenced::ManyToMany#<< appends a new document to the relation
rspec ./spec/functional/mongoid/relations/referenced/many_to_many_failing_spec.rb:37 # Mongoid::Relations::Referenced::ManyToMany#<< appends the existing document to the relation