Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Appliance drained and discharged
Disconnect inline connector to the flow switch and remove flow switch assembly

Measurement:

Measure the resistance across the pins of the inline connector which connects to the flow switch, whilst manually applying light pressure to the flow switch paddle.
Expected resistance continuity / zero resistance.
Note.
If there is no flow switch fitted on the appliance then select 'Resistance as expected'