Set Appliance State:

Mains Power Off
CH Demand
Ensure all heating controls are calling
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Mains reset switch On.
Allow boiler to fire and system to heat for a short period.
Turn OFF demand
Does the Burner extinguish and boiler shut down?
Note:
Pump may continue to run for a short period following end of demand.