Set Appliance State:

Mains Power Off
CH Demand
Isolate Mains Power to appliance as per TOPs P4
On/Off Switch On.
Connect a U-gauge to the Burner Pressure Test Point.
Gas On
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow the Boiler to purge itself and the Burner to ignite.
Run the Boiler until it reaches its operating temperature.
Does the Burner cut out when the User Thermostat is turned down and re-ignites when it is turned up?