code: protected function writePerformance($time)
      {
          $ms = round($time * 1000);
  
          foreach (self::$performanceThresholds as $colour => $threshold) {
              if ($ms > $threshold) {
                  break;
              }
          }
  
          $this->writeWithColor($colour, " ($ms ms)");
      }
docs: Writes the test performance metric formatted as the number of milliseconds elapsed.
  
  @param float $time Number of seconds elapsed.