You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: common.rb
    path of file: ./repos/ruby/spec/ruby/core/dir/fixtures
    
    the code of the file until where you have to start completion: # encoding: utf-8

module DirSpecs
  def self.mock_dir(dirs = ['dir_specs_mock'])
    @mock_dir ||= tmp("")
    File.join @mock_dir, dirs
  end

  def self.nonexistent
    name = File.join mock_dir, "nonexistent00"
    name = name.next while F
    
  def self.create_mock_dirs
    mock_dir_files.each do |name|
      file = File.join mock_dir, name
      mkdir_p File.dirname(file)
      touch file
    end
    mock_dir_links.each do |link, target|
      full_link = File.join mock_dir, link
      full_target = File.join mock_dir, target

      File.symlink full_target, full_link
    end
  end