An image forming method is disclosed. The test element group circuit includes a plurality of semiconductor devices connected in series between the first and second pads. A current flowing between the first ferromagnetic layer and the needle can be monitored, and thrusting of the needle can be interrupted when the current reaches a predetermined value. The assignment takes dynamically place at runtime. The force receiving end can receive an external force to move towards the circuit board about the bend point such that the two legs are driven to connect the common contact and the signal contact to form a conductive condition to output at least one command signal.