They do not drug test people at court session, no.
However, you're wrong about what is happening.
I suspect your first hearing was in JDR court since you weren't 18. Your appeal is not going to be in "civil" court but rather the "circuit court." That hearing is going to be a de novo trial. That is, a do over. The judge there is perfectly within his right to change the sentence after he finds you guilty again. That includes adding a probation period.
Judges have very little tolerance for going over 100 in Virginia. Jail time of 4-8 days (suspended down from 60) is a given. Probation and longer license suspensions are quite common. You could come out of this worse than when you went in. Also circuit court judges aren't typically the patient, friendly sort hte JDR judges are. You'd be well advised to have an attorney this time.