Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
CH Demand
Make sure there is a circulation path by opening up radiator valves
Remove the pump vent screw and take precautions to ensure any water released is safely contained
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Observe the pump, which will be on the system somewhere.
Is the pump running?
Note:
Do not take noise or vibration as confirmation that the pump is running.