JBZoo\Image\Image::addFilter PHP Method

    public function addFilter($filter)
    {
        $args = func_get_args();
        $args[0] = $this->_image;
        $newImage = null;
        if (is_string($filter)) {
            $filterClass = __NAMESPACE__ . '\\Filter';
            if (method_exists($filterClass, $filter)) {
                $newImage = call_user_func_array(array($filterClass, $filter), $args);
            } else {
                throw new Exception('Undefined Image Filter: ' . $filter);
            }
        } elseif (is_callable($filter)) {
            $newImage = call_user_func_array($filter, $args);
        }
        if (Helper::isGdRes($newImage)) {
            $this->_replaceImage($newImage);
        }
        return $this;
    }

 /**
  * @expectedException \JBZoo\Image\Exception
  */
 public function testFilterUndefined()
 {
     $img = new Image();
     $img->addFilter('undefined');
 }