OK so I was caught with less then an oz of marijuana a pipe and tobacco. And now I have to take a diversion class. Do my question is will I get tested when I go meet my diversion guy? Will I be tested for tobacco, marijuana and alcohol? Also how long will the class be? And by the way it's an MIP

Yes you may be tested. Diversion is often harder than regular probation (depending on the area)
They will test for, what ever the judge has ordered you, not to do.

First, any question on law needs to include your general locale because laws vary by area. And so do probation rules.

The ideas behind a diversion is to allow first time offenders to clean their record by doing some sort of service. When the service is completed, the conviction is removed from public record. In the case of drug use, it is very possible that testing will be part of the diversion requirement. But that is up to either the judge or the probation officer on your case. If I were in their position I would require it.