code: public function throwOn($method, $exception = false, $args = false)
      {
          $this->dieOnNoMethod($method, 'throw on');
          $this->actions->register($method, $args,
                  new SimpleThrower($exception ? $exception : new Exception()));
      }
docs: Sets up a trigger to throw an exception upon the method call.
  
  @param string $method     Method name to throw on.
  @param object $exception  Exception object to throw.
  If not given then a simple Exception object is thrown.
  @param array $args        Optional argument list filter.
  If given then the exception will only
  be thrown if the method call matches the arguments.