Display device including test element group, and method for inspecting defect of display device

A display device comprising:

• a substrate including a display area and a test area adjacent to the display area;
• a lower electrode disposed in the display area on the substrate;
• a light emitting layer disposed on the lower electrode;
• a common layer disposed on the light emitting layer;
• an upper electrode disposed on the common layer;
• and
• a test element group including:
• a plurality of electrode patterns disposed in a same layer as the lower electrode and in the test area on the substrate;
• a test common layer disposed in a same layer as the common layer and on the plurality of electrode patterns, wherein a plurality of openings is defined through the test common layer to expose a part of each of the plurality of electrode patterns;
• and
• an electrode layer disposed in a same layer as the upper electrode, on the test common layer, and in contact with the plurality of electrode patterns through the plurality of openings.