1. A test configuration comprising: a. a display panel including: i. a plurality of source lines; ii. a plurality of control lines; iii. a plurality of common lines; iv. a two-dimensional array of display elements, each display element including a transistor and a capacitor, wherein the transistor has a first current-handling terminal connected to one of the source lines, a second current-handling terminal, and a control terminal connected to one of the control lines, and wherein the capacitor has a first capacitor terminal connected to the second current-handling terminal and a second capacitor terminal connected to one of the common lines; b. an infrared detector positioned to receive infrared radiation from the display panel; and c. a signal generator having: i. a first test-signal output terminal connected to at least one of the source lines; ii. a second test-signal output terminal connected to at least one of the control lines; and iii. a third test-signal output terminal connected to at least one of the common lines.