A display device is disclosed. The device includes a display panel including a plurality of pixels including a first pixel electrically connected to a first data line and a second pixel electrically connected to a second data line. The display device also includes a current path switch configured to electrically connect the first pixel to the second pixel during a voltage drop test operation and electrically disconnect the first pixel from the second pixel during an image display operation. The display device further includes a voltage drop detector electrically connected to an end of the first data line and an end of the second data line, the voltage drop detector being configured to apply a test voltage to the end of the first data line and measure a dropped test voltage at the end of the second data line. The display device additionally includes a line resistance calculator.