Testing policies

Couple questions about workplace testing.

This is for the united states, and its reguarding the legality of drug testing.

Does an employer have to indicate that they do drug testing in some document, or are completely arbitrary tests acceptable. In other words, if I am hired by company x, and when I start I sign tons of papers. If there are no papers that I sign that say I understand I may be drug tested bla bla bla, is it legal to have a take the test or your fired ultimatem. There has yet to be a drug test at my job, I'm just wondering if I should ever worry about one.

Also, if a "random" test is done, who decides what "random" is. Is it legal to have a non-random testing. In otherwords, bob is suspected of stealing shit from company x, but no one can prove shit. On the surface bob looks like a solid guy. The company wants to get rid of him (or at least one of his bosses), but needs a legit reason. Can they say, bob your getting drug tested in hopes to have him sacked.

Ok, suppose you get caught with drugs in your system, will the company ever turn you over to police or just take disceplinary actions?

They can still test you. It dosent matter if you sign anything or not. Just like they can hire or fire you for any reason, even if they don't like the way you dress.

Random could mean anything, the emplyer could just say its random and test who ever he want's, or they could randomize it by say rolling a dice, or using a random number generation mathmatical equation. Thats the unfortunate reality of the issue.