private void createClientConnection(SecurityProtocol securityProtocol, String node) throws Exception {
        createSelector(securityProtocol, saslClientConfigs);
        InetSocketAddress addr = new InetSocketAddress("localhost", server.port());
        selector.connect(node, addr, BUFFER_SIZE, BUFFER_SIZE);
    }
Tests client connection close before response for authentication failure is sent.
clients/src/test/java/org/apache/kafka/common/security/authenticator/SaslAuthenticatorFailureDelayTest.java