[Analemma_]

> Has this not been done? If not, why?

I'm no libertarian, but I will concede that this is a perfect example of libertarian griping about government spending: it's not getting done because no one has any incentive for it to get done.

Does the manufacturer have any incentive to honestly test the machine? Hell no, then no one would buy it.

Does the government have any incentive to honestly test the machine? No, because airport/customs security is security theater and their goal is convincing voters that "something is being done". (Voters might have an incentive to honestly test the machine, but it's more-or-less impossible for this preference to affect policy, unless huge numbers of people become single-issue voters about security device testing. Which isn't likely.)

Do the operators have any incentive to honestly test the machine? No, because if a terrorist slips through the machine and then blows up a plane, none of the blame comes back to the individual officer who ran the test.

Without any incentive for the machine to work, it's no surprise that it doesn't.