RSpec - shared DB conn. & transactional fixtures not working - ruby-on-rails

Question

I tried to follow José Valim's advice on faster test suites, but to no avail.
I use Spork and put the AR monkey patch in the Spork.each_run block (see the spec helper below).
However, my request specs fail because the database is not cleaned between runs - specifically, I get errors such as expected 1 record, got X when doing assertions like Model.should have(1).record.
Update
The problem lies with request specs using Javascript. See the following spec - it fails when I use js: true, but not if I remove that (I use RSpec's config.treat_symbols_as_metadata_keys_with_true_values = true, fwiw.)
# encoding: UTF-8
require 'spec_helper'
feature "Create a shift", :js do
scenario %q(
In order to plan the workload
As a coordinator
I want to schedule shifts
And I want to see when they're scheduled for
) do
visit shifts_path
click_link "new_shift_#{Date.current}"
fill_in 'shift_note', with: 'Casper - luk'
click_link_or_button 'submit'
Shift.should have(1).record
Shift.last.begins_at.should == Date.current
page.should have_selector("ol[data-date=\"#{Date.current}\"] li#shift_#{Shift.last.id}")
end
end
I can tell it's related to the DB not being cleaned, because it fails the first time (expected 1 record, got 0), passes the second time (because there's 1 record in the DB) and then fails again on any subsequent runs (expected 1 record, got 2 etc.)
I'm trying to avoid using a gem like DatabaseCleaner, to keep dependencies as few as possible, and to avoid a speed decrease in the test suite.
Any help/info/pointers are greatly appreciated!
Relevant info:
Rails 3.2.2
RSpec 2.9.0
Capybara 1.1.2
Capybara-webkit 0.11.0
FactoryGirl 2.6.4
Spork 0.9.0
Guard 1.0.1
Guard-spork 0.5.2
on a Macbook Air, OS X 10.7.3 (if that's relevant)
And my spec helper:
# encoding: UTF-8
require 'rubygems'
require 'spork'
Spork.prefork do
ENV["RAILS_ENV"] ||= 'test'
require File.expand_path("../../config/environment", __FILE__)
require 'rspec/rails'
require 'capybara/rspec'
Dir[Rails.root.join("spec/support/**/*.rb")].each {|f| require f}
RSpec.configure do |config|
config.mock_with :rspec
config.use_transactional_fixtures = true
config.treat_symbols_as_metadata_keys_with_true_values = true
config.infer_base_class_for_anonymous_controllers = false
config.include Factory::Syntax::Methods
Capybara.javascript_driver = :webkit
Rails.logger.level = 4 # speed - http://blog.plataformatec.com.br/tag/capybara/
end
end
Spork.each_run do
require 'factory_girl_rails'
class ActiveRecord::Base
mattr_accessor :shared_connection
##shared_connection = nil
def self.connection
##shared_connection || retrieve_connection
end
end
ActiveRecord::Base.shared_connection = ActiveRecord::Base.connection
end

Answer 1

After much investigating, the problem seems to be with specs using JS in general, and not really the AR monkey patch.
I've re-phrased the problem in a new question here: RSpec+Capybara request specs w/ JS not working