Set Appliance State:

Set Boiler Control Thermostat to MAX position
CH Demand
Isolate Mains Power to appliance as per TOPs P4
Attach pressure gauge to burner pressure test point
External controls calling for heat
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Observation:

Allow fan to run and burner to ignite.
Does the pressure gauge show a burner pressure as per data badge?
(If you cannot read data badge click HERE for list of burner pressures)
Note:
When pressure gauge is removed pressure test point should be tightened & checked for gas soundness.