Set Appliance State:

Mains Power Off
CH Demand
Boiler Thermostat in its MAX position
Attach a temperature probe to the flow pipe from the appliance
(left hand pipe looking at the appliance from the front)
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Run the appliance and monitor the temperature of the flow pipe.
The temperature of the flow pipe should reach a maximum of approximately 82 degrees and then the burner should shut down as the boiler thermostat turns the burner off.
Note:
It may be necessary to reduce heating load by turning off some radiators to reduce time taken for this test.