Set Appliance State:

On/Off Switch OFF
Turn Hot Water Tap On
Isolate Mains Power to appliance as per TOPs P4
DHW temperature control set to maximum
Attach pressure 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

Observation:

Appliance On/Off control set to On position.
Reset lockout as necessary.
Allow the burner to ignite and establish.
Does the burner establish and reach maximum burner pressure of approximately 12.1 mbar?
Note:
When pressure gauge is removed pressure test point should be tightened & checked for gas soundness.