class Gem::Installer::FakePackage

def extract_files(destination_dir, pattern = "*")
  FileUtils.mkdir_p destination_dir
  spec.files.each do |file|
    file = File.join destination_dir, file
    next if File.exist? file
    FileUtils.mkdir_p File.dirname(file)
    File.open file, "w" do |fp|
      fp.puts "# #{file}"
    end
  end
end