A321 First Officer reported an unstable approach during a maintenance test flight resulted from improper use of automation. The flight became low and slow on the visual approach; and the pilot monitoring called for a go around; then flew another pattern and landed.

Narrative

Undesired aircraft state due to CRM breakdown and poor automation management.The following is the event how I remember it; which I know is not perfect.Flight was a executed as a routine test flight to evaluate VHF1 static on an Airbus NEO. Approach was briefed for the RNAV XX at ZZZ and mention was made that it would likely be a visual approach backed up by the RNAV. Descent checklist was executed per SOP. Upon return to the ZZZ area; controller queried whether the flight would like the RNAV XX or visual. PF elected to execute the visual with RNAV backup. Flight was cleared Direct ZZZ; which was roughly lined up with the RNAV XX (it seemed so easy at the time - PM even mentioned just going direct ZZZZZ; but did not do this; as it wasn't our clearance)Approx 20 miles from the field during a descent from 6 to 2 thousand; traffic was reported (and seen on TCAS) 11 o'clock ~4 miles; climbing to 2k and heading roughly the same direction but much slower. PM communicated around this time that we had loads of gas and if we need to knock off the approach and try again due to traffic; we could basically fly for the next 5 hours."Flight elected to level off at 3k' (ATC was aware) until the traffic was in sight and overtaken; then the flight was able to descend below the clouds (SCT - BKN layer at ~2.5k).Approx 10 miles from the field; PM reported 'field in sight' and flight was cleared for the visual approach to runway XX. APPR was selected; but PM had not properly sequenced (still direct ZZZ) the FMGC (first big error). PF called for Flaps 1 and F1 was selectedAs flight approached ~8 miles at ~2k' additional traffic was reported co-altitude at 11 o'clock for ~3 miles and closing. PM diverted attention to this traffic; PF continued to share focus on both the traffic and the approach. As PF dealt with the confusion of the approach not being sequenced correctly; it was around this time that PM became aware of the automation not looking correct and said something to the effect of; 'Just fly it.' PM's intent was to communicate for the PF to fly the approach manually; so what PM should have said was something like 'Click out; and fly pitch and thrust manually.' PF disconnected autopilot and took the throttles out of the CLB detent but did not disconnect autothrottles. PF then asked for PM to "set the altitude to minimums" or "TDZE" - PM then set something lower than should have been set based on how the box was sequenced (and based on SOP for that matter). At this point; PM was still diverting most attention to ensuring the flight did not need to go around for the traffic. PM does not recall whether airspeed was still managed or not. ~5-6 miles from the field; PM gained sight of traffic and flight was switched to tower. PM looked towards the runway and perceived a high rate of descent; crosschecking the instruments; ~2;500 ft/min ROD was noted. PM said something like 'you're over 2k' ft/min rate of descent.' As the flight approached 1;000' MSL; PM communicated the flight was too low. PM could tell PF was confused by the automation and asked "Do you want me to turn off your Flight Director?" Somewhere around this time (this event sequence may be slightly jumbled based on the time compression and stress) the aircraft got slow (~120 knots in F1; definitely in the yellow band below F1 maneuvering speed) and the "SPEED; SPEED; SPEED" aural alert sounded. PM noted that PF increased the throttle angle but failed to notice that there was not an associated increase in thrust (autothrottles were still engaged). Also at some point during this sequence; PF asked for more flaps; and PM selected Flaps 2 or 3. PF selected a higher thrust lever setting and the aircraft sped up and climbed. PM assessed a safe approach was not possible and stated; "I think we should go around." PF called for the go around and climbed into the landing pattern (1500' was set in the altitude box) and airspeed was selected at this point. Tower queried if the flight "would like to go back to Center;" but flight stayed with Tower executed a left closed pattern to a landing on runway XX."