What type of plate boundary would you expect at a strike - slip fault?

At a strike - slip fault, you would except a transform plate boundary.

Explanation:

Strike slip faults are the faults where the huge pieces of rocks move in opposite direction of each other but they move in horizontal direction only. Such faults are formed when these pieces of rocks they move in opposite direction of each other.

It occurs only at the plate boundaries which are transform plate boundaries. One of the biggest example of the transform plate boundary is the San Andrea's fault in the city of California. These faults are mostly fractures in the blocks.