public function assertResponseReasonPhraseIs($phrase) {
        $this->requireResponse();

        try {
            Assertion::same($phrase, $actual = $this->response->getReasonPhrase(), sprintf(
                'Expected response reason phrase "%s", got "%s".',
                $phrase,
                $actual
            ));
        } catch (AssertionFailure $e) {
            throw new AssertionFailedException($e->getMessage());
        }
    }