Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
CH Demand
Gas On; Pilot On
Boiler On/Off Switch OFF
CH Switch ON
DHW Switch in INSTANT position
CH Temperature Control in Maximum position
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Observation:

Switch on the boiler ON/OFF switch while observing the pump flow valve spindle.
With the CH demand the pump flow valve spindle should fully extend and operate stage 1 of the gas valve.