Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
DHW temperature control to maximum
CH temperature control to minimum
Loosen the outlet test point screw (P2) and attach U-gauge to the test point
Gas On
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Does the burner light and go to maximum burner pressure (approximately 35.4mb for Propane, 27.2mb for Butane) after a few seconds?
Isolate Mains Power to appliance as per TOP's P4
Disconnect one wire from the appliance modureg
Mains power On
Does the burner light at minimum burner pressure (approximately 6.1mb for Propane, 4.7mb for Butane) after a few seconds?
Note:
When pressure gauge is removed the pressure test point should be tightened and checked for gas tightness.