A system 100 for testing light-emitting diode (LED) displays is disclosed. The system is implemented within a portable handheld housing and includes a computing module 102, a test module 104, and an adaptor module 106. The computing module 102 includes a rechargeable battery 118 for providing electrical power to the system; a processor 122 for running operational software for testing an LED display 108; and a user interface 114 that allows a user to select from multiple test options for testing the LED display and that displays measured operational attributes of the display to the user. The test module 104 includes a nonvolatile memory unit for storing test images to be displayed on the LED display, and a data acquisition and control circuit for communicating power and control signals for displaying the test images on the LED display, and for measuring operational attributes of the LED display. The adaptor module 106 is adapted to be selectively and communicatively coupled to the LED display 108, and to automatically to identify the type of LED display attached. The adaptor module 106 communicates the display type to computing module 102, which uses the type to determine test options available for the LED display 108 and to select corresponding test images and power and control signals to communicate to the LED display 108.