Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
Gas On; Pilot On
Boiler On/Off Switch ON
CH Switch OFF
DHW Switch in INSTANT position
Remove solenoid from gas valve - do NOT disconnect the leads from the solenoid, solenoid can be stood upright on control box. The solenoid spindle should be in its retracted position
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Observation:

The solenoid spindle should rise fully (approximately 8mm of the spindle should be visible when fully extended) with the hot water demand.
Boiler On/Off Switch OFF.
Spindle should smoothly move back to its retracted position.