boot.rb

class Rails::Boot
  def run
    load_initializer
    extend_environment
    Rails::Initializer.run(:set_load_path)
  end

  def extend_environment
    Rails::Initializer.class_eval do
      old_load = instance_method(:load_environment)
      define_method(:load_environment) do
        groups = [:default, Rails.env.to_sym]
        groups << :development_test_cucumber if %w(development test cucumber).include?(Rails.env)
        groups << :test_cucumber if %w(test cucumber).include?(Rails.env)
        groups << :test_osx if Rails.env.test? && RUBY_PLATFORM =~ /darwin/
        Bundler.require groups
        old_load.bind(self).call
      end
    end
  end
end

Gemfile

source :gemcutter

gem 'rails', '2.3.5'
gem 'httparty'
gem 'mad_mimi_mailer', '0.0.8'
gem 'fastercsv'
gem 'crummy'
gem 'prawn'
gem 'barby'
gem 'friendly_id'
gem 'haml'
gem 'sqlite3-ruby'
gem 'aws-s3'

group :development_test_cucumber do
  gem 'ruby-debug'
end

group :test_cucumber do
  gem 'rspec',            :require => nil
  gem 'rspec-rails',      :require => nil
  gem 'factory_girl'
  gem 'faker'
  gem 'fakeweb'
  gem 'spork',            :require => nil
end

group :test do
  gem 'remarkable_rails', :require => nil
  gem 'nulldb',           :require => 'nulldb_rspec'
  gem 'ZenTest'
  gem 'autotest-rails'
end

group :test_osx do
  # These make autotest work better on OS X, but don't work on other platforms.
  gem 'autotest-growl',   :require => nil
  gem 'autotest-fsevent', :require => nil
end

group :cucumber do
  gem 'cucumber',         :require => nil
  gem 'cucumber-rails',   :require => nil
  gem 'capybara',         :require => nil
  gem 'database_cleaner', :require => nil
  gem 'launchy',          :require => nil
  gem 'pickle',           :require => nil
end