A display device includes a display panel having a glass substrate, a first input pad formed on the glass substrate and a second input pad formed on the glass substrate, and a driver integrated circuit mounted on the glass substrate of the display panel using a chip-on-glass (COG) method. The driver integrated circuit includes first and second input bumps respectively coupled to the first and second input pads, and an internal ground line coupled to the first and second input bumps. The first input bump of the driver IC receives a test signal through the first input pad when a COG bonding test is performed, and receives a ground voltage when the display device operates.