AccessTokenRetriever getAccessTokenRetriever() {
        return accessTokenRetriever;
    }
@Test
    public void testConfigureWithAccessTokenFile() throws Exception {
        String expected = "{}";

        File tmpDir = createTempDir("access-token");
        File accessTokenFile = createTempFile(tmpDir, "access-token-", ".json", expected);

        OAuthBearerLoginCallbackHandler handler = new OAuthBearerLoginCallbackHandler();
        Map<String, ?> configs = getSaslConfigs(SASL_OAUTHBEARER_TOKEN_ENDPOINT_URL, accessTokenFile.toURI().toString());
        Map<String, Object> jaasConfigs = Collections.emptyMap();
        configureHandler(handler, configs, jaasConfigs);
        assertInstanceOf(FileTokenRetriever.class, handler.getAccessTokenRetriever());
    }