Technically, "random" is a loaded term with many different meanings as to how it is generated and how that term is applied. If you are being tested by a court ordered process, by probation, or some other inflicted regime then your main concern should be to not let them catch you with dirty urine by staying clean.
Often, a court ordered "random' test simply means that YOU will not know when it is coming, not that it is fairly distributed among time or other persons. Whether the frequency of the tests is dependent upon your being of a certain race or religion or because a probation officer is trying to "catch you" using should be irrelevant to you. The way to beat them regardless of the reason is to simply stay clean. Once you stay clean and prevail in that particular requirement, then you can go and examine whether it was fairly applied or not and, if applicable, make some noise about it. Until then, your protests will not make much of an impression on anyone in a position to help you.
Now, this is not legal advice. It is more like friendly advice. I understand you think you are being discriminated against, but like I said, "random" in this context isn't as much about statistical frequency as much as it is about "surprise." That being said, a simple coin tossing experiment might show that it is perfectly reasonable to expect that out of X tosses you will get certain repeats of three even while accepting that tossing a coin is a good example of randomly getting either test (heads) or no test (tails).
Save your energy though, just stay clean and pass the tests.