I had a few beers on Wednesday and had a random drug test Thursday

24 hours, I believe. You're screwed.

Agree, what type of test is it for, work, to see if you are drunk right then, ( since for work you can drink the night before)

Is it for children and family services about custody, is it from probation or parole ?

If the test was for urine alcohol (EtOH) then you can multiply the number of drinks you consumed by 2. The result is the maximum number of hours required for clearance*. Of course EtOH remains in your bladder until you urinate.

As FrChuck noted the type of test is important. If the test was for EtG, a metabolite of alcohol, then that would still be detectable at 24 hours or longer. EtG testing is used only when an individual is required to remain totally abstinent.....no drinking allowed!

*if your drinking time exceeds three (3) hours this formula can result in a substantial over estimate of clearance time required but never an under estimate.