master gardner pre-test
A pretest is usually a way to find out how much knowledge you already have concerning plants and gardening in this case.
If they are using it for any other purpose then they are using it wrong. You should not need to prepare for a pretest unless they have told you that you need to do so for some other reason.
Pre tests usually help instructors determine what they need to emphasize during the training sessions. It helps in determining the handouts and dealing with misconceptions that some may have concerning plants.