Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to AC Volts Set meter to measure AC Volts
CH Demand
Locate the pump and remove its electrical compartment cover
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Reset boiler as required.
Measure the voltage across the L and N connections of the pump.
Expect mains voltage.