public function addOnFulfilled(callable $callback): void
    {
        if ($this->getState() === Promise::PENDING) {
            $this->onFulfilled[] = $callback;
        } elseif ($this->getState() === Promise::FULFILLED) {
            $response = call_user_func($callback, $this->responseBuilder->getResponse());
            if ($response instanceof ResponseInterface) {
                $this->responseBuilder->setResponse($response);
            }
        }
    }