An automated test system was developed to characterize detectors for the Kilopixel Array Pathfinder Project (KAPPa), a 16-pixel 2D integrated heterodyne focal plane array. Although primarily designed for KAPPa, the system can be used with other instruments to automate tests that might be tedious and time-consuming by hand. Mechanical components include an adjustable structure of aluminum t-slot framing that supports a rotating chopper. Driven by a stepper motor, the wheel alternates between blackbodies at room temperature and 77 K. The cold load consists of absorbing material submerged in liquid nitrogen in an open Styrofoam cooler. Python scripts control the mechanical system, interface with receiver components, and process data. Test system operation was verified by sweeping the local oscillator frequency with a Virginia Diodes room temperature receiver. The system was then integrated with the KAPPa receiver to allow complete and automated testing of all array pixels with minimal user intervention.