old_contents: const dns = jest.genMockFromModule('dns')
  
  function lookup(hostname, options, callback = jest.fn()) {
    let cb = callback
    if (typeof options === 'function') {
      cb = options
    }
    process.nextTick(cb, null, hostname)
  }
  
  dns.lookup = lookup
  
  module.exports = dns
  
new_contents: const dns = jest.genMockFromModule('dns')
  
  /**
   * lookup - Mock lookup.
   *
   * @param  {string} hostname Hostname
   * @param  {object} options Options
   * @param  {Function} callback Callback
   */
  function lookup(hostname, options, callback = jest.fn()) {
    let cb = callback
    if (typeof options === 'function') {
      cb = options
    }
    process.nextTick(cb, null, hostname)
  }
  
  dns.lookup = lookup
  
  module.exports = dns
  
subject: fix jsdoc issues in test dir