# File lib/bundler/runtime.rb, line 12
    def setup(*groups)
      @definition.ensure_equivalent_gemfile_and_lockfile if Bundler.frozen_bundle?

      groups.map!(&:to_sym)

      # Has to happen first
      clean_load_path

      specs = groups.any? ? @definition.specs_for(groups) : requested_specs

      SharedHelpers.set_bundle_environment
      Bundler.rubygems.replace_entrypoints(specs)

      # Activate the specs
      load_paths = specs.map do |spec|
        unless spec.loaded_from
          raise GemNotFound, "#{spec.full_name} is missing. Run `bundle install` to get it."
        end

        check_for_activated_spec!(spec)

        Bundler.rubygems.mark_loaded(spec)
        spec.load_paths.reject {|path| $LOAD_PATH.include?(path) }
      end.reverse.flatten

      # See Gem::Specification#add_self_to_load_path (since RubyGems 1.8)
      if insert_index = Bundler.rubygems.load_path_insert_index
        # Gem directories must come after -I and ENV['RUBYLIB']
        $LOAD_PATH.insert(insert_index, *load_paths)
      else
        # We are probably testing in core, -I and RUBYLIB don't apply
        $LOAD_PATH.unshift(*load_paths)
      end

      setup_manpath

      lock(:preserve_unknown_sections => true)

      self
    end