"Random" Testing

So on Tuesday of this week I was randomly selected to be drug tested. Our company does "random" drug tests about every 4 to 5 weeks. They test about 30 people each time. I have worked their for 2 years and this is my first time being selected. So when the lady from HR came to tell me I was picked and needed to go pee in a cup I laughed because I had just gone to the bathroom 20 minutes before. My co-worker and I had just been talking about being picked for the drug test just right after you go to the bathroom and then it happened to me. Funny how it always works out that way. So I went down to the bathroom where the technicians were and I drank a little water and then went for the gold. Sadly on my first attempt I did not have enough pee. So I had to throw away that sample and start drinking lot's of water. I sat around for about 45 minutes drinking 4 glasses of water and hanging out in the little lounge area with some other co-workers until we felt like we could give enough of a sample. On my second attempt I had more than enough fluid. Then about 20 minutes after the test I had to go to the bathroom and then after I went, about another 30 minutes later I had to go again. FYI: As far as I know I passed because I still have a job, but I'm not worried.