There are various ways you can test it. But it obviously depends on what the mechanism is. If you’re cutting physical wires used to raise or lower something then hopefully it is obvious the mechanism will work (but maybe it goes wrong if the cut end of the wire is caught somewhere.)

In a computer system, you ought to be able to test systems to make sure they behave correctly under the consequences of a switch press. You could also test them—there may be times when it is ok to press the switch, or where you have redundancy such that two switches must be pressed but you only press one to test.

But I think another alternative is to not have the mechanism used extremely rarely. I think it can be good to accept cases where things go wrong a bit from time to time so that people have practice dealing with them as the alternative is to only have things go wrong under some enormous catastrophe when no one will have any idea what to do.