They will do any kind of drug testing and it is almost always done randomly. They will test for any substance using any method. The most common two methods that are most often used are blood testing or urine analysis. However sometimes if they believe you are taking a substance and they still aren't picking it up they will do breath tests, hair tests, skin tests, sweat tests, etc. Most of the random drug tests are done out there in the field. They will usually higher a nurse from a local clinic or hospital to go out an collect blood or urine samples. Usually on pre-announced tests you will have to go physically to the clinic yourself. But anyways they will test for all substances and can use any form of testing they want, but most often they will do either blood or urine tests.