code: public function makeDry($is_dry = true)
      {
          $numberOfReporters = count($this->reporters);
          for ($i = 0; $i < $numberOfReporters; $i++) {
              $this->reporters[$i]->makeDry($is_dry);
          }
      }
docs: Signals that the next evaluation will be a dry run.
  That is, the structure events will be recorded, but no tests will be run.
  
  @param bool $is_dry        Dry run if true.