QoS 0 in puback?

[gnought]

QoS 0 in puback in https://github.com/mqttjs/mqtt-packet/blob/master/test.js#L1072 ?
It seems that packet is generated from a template https://github.com/mqttjs/mqtt-packet/blob/master/packet.js
and it will appear in the packet variable in https://github.com/mqttjs/mqtt-connection/blob/master/test/connection.parse.js#L365

A little bit confusion