Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove the microswitch from the hydroblock
Remove the wires from the terminals

Measurement:

Measure the resistance between the 2 outer terminals of the microswitch (do not press the microswitch the pin must be released).
Expect continuity/zero resistance.
Is the resistance measured as expected?