public static MqttMessage newMessage(MqttFixedHeader mqttFixedHeader, Object variableHeader, Object payload) {
        switch (mqttFixedHeader.messageType()) {
            case CONNECT :
                return new MqttConnectMessage(
                        mqttFixedHeader,
                        (MqttConnectVariableHeader) variableHeader,
                        (MqttConnectPayload) payload);

            case CONNACK:
                return new MqttConnAckMessage(mqttFixedHeader, (MqttConnAckVariableHeader) variableHeader);

            case SUBSCRIBE:
                return new MqttSubscribeMessage(
                        mqttFixedHeader,
                        (MqttMessageIdVariableHeader) variableHeader,
                        (MqttSubscribePayload) payload);

            case SUBACK:
                return new MqttSubAckMessage(
                        mqttFixedHeader,
                        (MqttMessageIdVariableHeader) variableHeader,
                        (MqttSubAckPayload) payload);

            case UNSUBACK:
                return new MqttUnsubAckMessage(
                        mqttFixedHeader,
                        (MqttMessageIdVariableHeader) variableHeader,
                        (MqttUnsubAckPayload) payload);

            case UNSUBSCRIBE:
                return new MqttUnsubscribeMessage(
                        mqttFixedHeader,
                        (MqttMessageIdVariableHeader) variableHeader,
                        (MqttUnsubscribePayload) payload);

            case PUBLISH:
                return new MqttPublishMessage(
                        mqttFixedHeader,
                        (MqttPublishVariableHeader) variableHeader,
                        (ByteBuf) payload);

            case PUBACK:
                //Having MqttPubReplyMessageVariableHeader or MqttMessageIdVariableHeader
                return new MqttPubAckMessage(mqttFixedHeader, (MqttMessageIdVariableHeader) variableHeader);
            case PUBREC:
            case PUBREL:
            case PUBCOMP:
                //Having MqttPubReplyMessageVariableHeader or MqttMessageIdVariableHeader
                return new MqttMessage(mqttFixedHeader, variableHeader);

            case PINGREQ:
            case PINGRESP:
                return new MqttMessage(mqttFixedHeader);

            case DISCONNECT:
            case AUTH:
                //Having MqttReasonCodeAndPropertiesVariableHeader
                return new MqttMessage(mqttFixedHeader,
                        variableHeader);

            default:
                throw new IllegalArgumentException("unknown message type: " + mqttFixedHeader.messageType());
        }
    }
@Test
    public void createUnsubAckV3() {
        MqttFixedHeader fixedHeader =
                new MqttFixedHeader(MqttMessageType.UNSUBACK, false, MqttQoS.AT_MOST_ONCE, false, 0);
        MqttMessageIdVariableHeader variableHeader =
                MqttMessageIdVariableHeader.from(SAMPLE_MESSAGE_ID);

        MqttMessage unsuback = MqttMessageFactory.newMessage(fixedHeader, variableHeader, null);

        assertEquals(MqttMessageType.UNSUBACK, unsuback.fixedHeader().messageType());
        MqttMessageIdAndPropertiesVariableHeader actualVariableHeader =
                (MqttMessageIdAndPropertiesVariableHeader) unsuback.variableHeader();
        assertEquals(SAMPLE_MESSAGE_ID, actualVariableHeader.messageId());
        validateProperties(MqttProperties.NO_PROPERTIES, actualVariableHeader.properties());
        MqttUnsubAckPayload actualPayload = (MqttUnsubAckPayload) unsuback.payload();
        assertNotNull(actualPayload);
        assertEquals(0, actualPayload.unsubscribeReasonCodes().size());
    }