Set Appliance State:

Gas Off
Isolate Mains Power to appliance as per TOPs P4
CH Demand
Attach pressure gauge to inlet pressure test point
External controls calling
Gas On
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Reset boiler as necessary.
Allow ignition sequence to commence and sparking to occur.
Does the pressure gauge show an inlet pressure of at least 18 mb throughout the sequence?
Note:
When pressure gauge is removed pressure test point should be tightened & checked for gas soundness.