code: protected function outsideMessage($compare)
      {
          $dumper = $this->getDumper();
  
          if ($compare > $this->upper) {
              return 'Outside expectation ' .
                      $dumper->describeDifference($compare, $this->upper);
          } else {
              return 'Outside expectation ' .
                      $dumper->describeDifference($compare, $this->lower);
          }
      }
docs: Creates a the message for being within the range.
  
  @param mixed $compare        Value being tested.