function guid() {
  function s4() {
    return Math.floor((1 + Math.random()) * 0x10000)
      .toString(16)
      .substring(1);
  }
  return s4() + s4() + '-' + s4() + '-' + s4() + '-' + s4() + '-' + s4() + s4() + s4();
}

module.exports = function(cb) {
  cb = cb || function() {};

  var id   = guid(),
      name = 'test-lambda';

  var succeed = function(result) { cb(null, result) };
  var error   = function(error)  { cb(error, null) };

  return {
    awsRequestId:    id,
    invokeid:        id,
    logGroupName:    '/aws/lambda/' + name,
    logStreamName:   '2015/09/22/[HEAD]13370a84ca4ed8b77c427af260',
    functionVersion: 'HEAD',
    isDefaultFunctionVersion: true,

    functionName:    name,
    memoryLimitInMB: '1024',
    functionVersion: 'HEAD',

    succeed:         succeed,
    fail:            error,
    done:            cb,

    getRemainingTimeInMillis: function() {
      return 5000;
    }
  }
}