The embodiments of the present invention enable a new metal diagnosis pattern based on a production test pattern to quickly identify open and short circuits of metal lines which cannot be probed, such as the long lines of a programmable logic device, and to further isolates the fault location for physical failure analysis. According to one aspect of the invention, a circuit locally drives a plurality of metal long line segments to determine whether a defect in a line is a short circuit, or further to identify the location of an open circuit.