According to other blogs etc it was a route check for the crew who's taking the Chinese Premier down there later this week, as they don't want to take the 747 in there.
We mentioned a few days ago the arrival of Air China's Boeing 737-800 B-1761 into Auckland from Guangzhou via Darwin as CCA002A. It then conducted a training/route proving flight to Wellington and back 25 March before ultimately carrying Chinese Premier Li Keqiang late on the afternoon of 26 March after he and associated delegation arrived in Auckland from Sydney onboard Air China Boeing 747-400 B-2447 as CCA002.
The Boeing 737-800 returned to Auckland from Wellington 27 March and departed mid afternoon 28 March for Sydney, then flew onto Darwin and Guangzhou 29 March while the Boeing 747-400 departed Auckland mid morning 29 March for Peking.
Found this on MRC ( I think Air China maybe come a regular flight service to Welly