A test system (10) for testing an electric device (30), in particular a high-voltage device, has a portable main device (100) with a housing (140), an electric connection assembly (120, 121) and a mechanical connection assembly (145) and has a portable additional device (200, 300) with a separate housing (240, 340), an electric connection assembly (220, 320) and a mechanical connection assembly (245). The main device (100) can be mechanically connected to the additional device (200, 300) in a releasable manner by coupling the mechanical connection assemblies (145, 245) to form a structural unit, wherein the main device (100) can be electrically connected to the additional device (200, 300) via the first electric connection assemblies (120, 121, 220, 320).