Set Appliance State:

Mains Power Off
Gas Off
CH Demand
Selector switch to CH
Ensure pump is at MAX speed setting
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Does the pump run satisfactorily?
Note:
Do not take vibration as an indication of pump running, if pump vent plug is removed to observe pump shaft turning then care should be taken water does not drip onto the boiler electrics.