private TestJaasConfig configureMechanisms(String clientMechanism, List<String> serverMechanisms) {
        saslClientConfigs.put(SaslConfigs.SASL_MECHANISM, clientMechanism);
        saslServerConfigs.put(BrokerSecurityConfigs.SASL_ENABLED_MECHANISMS_CONFIG, serverMechanisms);
        if (serverMechanisms.contains("DIGEST-MD5")) {
            saslServerConfigs.put("digest-md5." + BrokerSecurityConfigs.SASL_SERVER_CALLBACK_HANDLER_CLASS_CONFIG,
                    TestDigestLoginModule.DigestServerCallbackHandler.class.getName());
        }
        return TestJaasConfig.createConfiguration(clientMechanism, serverMechanisms);
    }
Tests client connection close before response for authentication failure is sent.
clients/src/test/java/org/apache/kafka/common/security/authenticator/SaslAuthenticatorFailureDelayTest.java