Set Appliance State:

Mains Power Off
CH Demand
Boiler mains switch On
Boiler CH thermostat to maximum
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Allow burner to ignite and run.
Does the CH flow pipe and system heat correctly?
Also monitor the system pressure as the CH warms up.