If you don't pull any load on the motors (don't stall them) then the driver will make the motors spin.
Once the load becomes enough to draw more than 2A, one of two things will happen:
1) The Ardumotor will overheat and destroy itself.
2) The Ardumotor will detect and prevent over-current, and the motors won't run.
You really want to match the motors to your controller; if the controller is too weak, you will never be happy with the result.