code: function () {
      var self = this;
  
      return new Promise(function (resolve, reject) {
        self.mocha = new Mocha({
          ui       : 'bdd',
          reporter : path.join(__dirname, '../reporters/mocha_worker_reporter'),
          slow     : process.env.WORKER_SLOW || self.SLOW,
          timeout  : process.env.WORKER_TIMEOUT || self.TIMEOUT,
          bail     : true
        });
  
        self.mocha.addFile(process.env.WORKER_TEST);
  
        self.runner = self.mocha.run(function (failures) {
          resolve();
        });
  
        self.runner.on('suite', function (suite) {
          self.totalTests = suite.total;
        });
  
        self.runner.on('test end', function () {
          self.testsFinished++;
          self.checkMemory();
        });
  
        self.runner.on('fail', function () {
          self.hasFailingTest = true;
        });
  
        self.runner.on('end', function () {
          self.checkFinishedTests();
          self.checkTestCount();
          self.checkMemory();
  
          process.send({
            type : 'suiteDone',
            data : process.env.WORKER_TEST
          });
  
          cluster.worker.kill(0);
        });
      });
    }
docs: ////////////////////////////////////////////////////////////////////////// Public methods ///////////////////////////////////////////////////////// //////////////////////////////////////////////////////////////////////// 
  MochaRunner.start() -> Object