Joe McCarthy wrote on Feb 1^st, 2017 at 3:03am:

Why do people do infidelity tests?  Ugh.... They cause more damage than they do good, unless done under the management of a therapist, and used for the purposes thereof.  Frankly, the money is better spent on a therapist, or a lawyer. No one, NO ONE, comes away from an infidelity test a winner. Both parties ALWAYS walk away more hurt than when they walk in, and nothing gets solved.

I'm thinking that one reason for this, in addition to the mythology about the "amazing" infallibility of the polygraph so deeply instilled in our popular culture, is the sad fact that the male partner may be afraid (not without reason) of the financial consequences of a divorce.
Hence, the man will resort to anything to "prove" his renewed  fidelity. ::)