error in blog sample app in @avdi's Objects on Rails with nulldb setup!!!

error_because_of_nulldb_requiring

/home/jesus/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.0.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:8:in `<module:ActiveRecord>': uninitialized constant ActiveRecord::ConnectionNotEstablished (NameError)
	from /home/jesus/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.0.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:5:in `<top (required)>'
	from /home/jesus/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:55:in `require'
	from /home/jesus/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:55:in `require'
	from /home/jesus/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-3.0.0/lib/active_record/connection_adapters/abstract_adapter.rb:11:in `<top (required)>'
	from /home/jesus/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:55:in `require'
	from /home/jesus/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:55:in `require'
	from /home/jesus/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-nulldb-adapter-0.2.1/lib/active_record/connection_adapters/nulldb_adapter.rb:4:in `<top (required)>'
	from /home/jesus/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:55:in `require'
	from /home/jesus/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:55:in `require'
	from /home/jesus/.rvm/gems/ruby-1.9.2-p0/gems/activerecord-nulldb-adapter-0.2.1/lib/nulldb_rspec.rb:1:in `<top (required)>'
	from /home/jesus/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:59:in `require'
	from /home/jesus/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:59:in `rescue in require'
	from /home/jesus/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:35:in `require'
	from /home/jesus/Rails Applications/blog_objects_rails/spec/spec_helper_lite.rb:2:in `<top (required)>'
	from /home/jesus/Rails Applications/blog_objects_rails/spec/models/post_spec.rb:1:in `require_relative'
	from /home/jesus/Rails Applications/blog_objects_rails/spec/models/post_spec.rb:1:in `<top (required)>'
	from /home/jesus/.rvm/gems/ruby-1.9.2-p0/gems/rspec-core-2.0.1/lib/rspec/core/configuration.rb:306:in `load'
	from /home/jesus/.rvm/gems/ruby-1.9.2-p0/gems/rspec-core-2.0.1/lib/rspec/core/configuration.rb:306:in `block in load_spec_files'
	from /home/jesus/.rvm/gems/ruby-1.9.2-p0/gems/rspec-core-2.0.1/lib/rspec/core/configuration.rb:306:in `map'
	from /home/jesus/.rvm/gems/ruby-1.9.2-p0/gems/rspec-core-2.0.1/lib/rspec/core/configuration.rb:306:in `load_spec_files'
	from /home/jesus/.rvm/gems/ruby-1.9.2-p0/gems/rspec-core-2.0.1/lib/rspec/core/command_line.rb:18:in `run'
	from /home/jesus/.rvm/gems/ruby-1.9.2-p0/gems/rspec-core-2.0.1/lib/rspec/core/runner.rb:55:in `run_in_process'
	from /home/jesus/.rvm/gems/ruby-1.9.2-p0/gems/rspec-core-2.0.1/lib/rspec/core/runner.rb:46:in `run'
	from /home/jesus/.rvm/gems/ruby-1.9.2-p0/gems/rspec-core-2.0.1/lib/rspec/core/runner.rb:10:in `block in autorun'

Gemfile

source 'http://rubygems.org'

gem 'rails', '3.0.0'
gem 'sqlite3-ruby', :require => 'sqlite3'

group :development do
  gem 'rspec-rails', '2.0.1'
end

group :test do
  gem 'rspec', '2.0.1'
  gem 'webrat', '0.7.1'
  gem 'activerecord-nulldb-adapter', '0.2.1'
end

post_spec.rb

require_relative '../spec_helper_lite'
require_relative '../../app/models/post'

describe Post do

  before do
    setup_nulldb
    ...
  end

  after do
    teardown_nulldb 
  end

...
end

spec_helper_lite_only_requiring_nulldb.rb

require 'date'
require 'nulldb_rspec'

def require_folder(folder_name_in_app)
  Dir[File.expand_path(File.dirname(__FILE__) + '/../app/' + folder_name_in_app + '/*.rb')].each { |file| require file }
end

spec_helper_lite_with_setup_and_teardown_nulldb.rb

require 'nulldb_rspec'

def setup_nulldb
  schema_path = File.expand_path("../db/schema.rb/", File.dirname(__FILE__))
  ActiveRecord::Base.establish_connection(:adapter => :nulldb, :schema => schema_path) # I tried without setting :schema option also I tried without this whole line
                                                                                       # also because of ActiveRecord::Base I required 'active_record' but I got no                                                                                                                                                                                
                                                                                       # method error for nullify in NullDB module and also it became so slow because      
                                                                                       # of requiring 'active_record' again
  NullDB.nullify(:schema => schema_path)
end

def teardown_nulldb
  NullDB.restore
end

def require_folder(folder_name_in_app)
  Dir[File.expand_path(File.dirname(__FILE__) + '/../app/' + folder_name_in_app + '/*.rb')].each { |file| require file }
end