I worked for a company for about 5 years. The 4th year I was there they sent everyone a form to sign, consenting to random tests. They implemented the program about 2 months after they passed out the forms.

There were about 200 employees and only one person (a driver) was tested within a couple of months after they implemented this program. I know people that still work there and haven't heard of anyone else being tested.

It seems like they did that, primarily, as a threat.