A display panel includes an insulation substrate having a display area and a peripheral area, wires disposed on the insulation substrate in the display area, first and second testing lines disposed on the insulation substrate and aligned substantially parallel to each other, and a diode unit disposed between the wires and one of the first testing line and the second testing line. The wires extend from the display area into the peripheral area and through diodes included in the diode unit, and the wires are electrically connected to the one of the first testing line and the second testing line.