Xpressengine\Presenter\Html\FrontendHandler::output PHP Method

    public function output()
    {
        $args = func_get_args();
        $name = array_shift($args);
        if (!isset($this->tags[$name])) {
            // TODO: throw Exception
            return;
        }
        $class = $this->tags[$name];
        return forward_static_call_array([$class, 'output'], $args);
    }

 public function testOutput()
 {
     $tags = $this->getTagList();
     $frontend = new FrontendHandler($tags);
     $output = $frontend->output('js', 'body.prepend');
 }