@Test
    public void illegalToken() throws Exception {
        byte[] bytes = saslServer.evaluateResponse(clientInitialResponse(null, true, Collections.emptyMap()));
        String challenge = new String(bytes, StandardCharsets.UTF_8);
        assertEquals("{\"status\":\"invalid_token\"}", challenge);
    }
If the callback handler handles the `OAuthBearerExtensionsValidatorCallback`
 and finds an invalid extension, SaslServer should throw an authentication exception
clients/src/test/java/org/apache/kafka/common/security/oauthbearer/internals/OAuthBearerSaslServerTest.java