    # File lib/rubygems/test_utilities.rb, line 59
      def download spec, source_uri, install_dir = Gem.dir
        name = "#{spec.full_name}.gem"
        path = File.join(install_dir, 'cache', name)

        Gem.ensure_gem_subdirectories install_dir

        if source_uri =~ /^http/ then
          File.open(path, "wb") do |f|
            f.write fetch_path(File.join(source_uri, "gems", name))
          end
        else
          FileUtils.cp source_uri, path
        end

        path
      end