code: public function renderShadowMark($count, $current, $eolInterval = 60)
      {
          $this->progressCount++;
          $this->write('<fg=blue;options=bold>S</fg=blue;options=bold>', false);
          if (($this->progressCount % $eolInterval) == 0) {
              $counter = str_pad($this->progressCount, 5, ' ', STR_PAD_LEFT);
              $this->write(
                  ' |' . $counter . ' ('
                  . str_pad($current, strlen($count), ' ', STR_PAD_LEFT)
                  . '/' . $count . ')' . PHP_EOL,
                  false
              );
          }
      }
docs: Render a shadow marker, i.e. a mutation whose source code line is
  not covered by any test based on current code coverage data.
  
  @param int $count
  @param int $current
  @param int $eolInterval