A test system for testing an electric device (30, 34), comprising: a portable main device with a first housing and a first mechanical connection assembly disposed on the first housing and a first electric connection assembly (120, 121) disposed on the first housing, and a portable additional device (200, 300), separate from the portable main device, with a second housing (240, 340) and a second mechanical connection assembly disposed on the second housing and a second electric connection assembly (220, 320) disposed on the second housing, wherein the portable main device can be mechanically connected to the portable additional device (200, 300) in a releasable manner by coupling the first mechanical connection assembly to the second mechanical connection assembly to form a structural unit, and wherein the portable main device can be electrically connected to the portable additional device (200, 300) via the first electric connection assembly (120, 121) and the second electric connection assembly (220, 320), characterized in that the portable main device has a power-amplifying device for generating a power signal which is to be transmitted to the portable additional device (200, 300) via the first electric connection assembly (120, 121) and the second electric connection assembly (220, 320), that the portable additional device (200, 300) has a test signal apparatus for generating a test signal, which is to be output to the electric device (30, 34), on the basis of the power signal of the portable main device, and that the portable main device has a measuring device for measuring a measurement variable of the electric device (30, 34) as a test response to the test signal of the portable additional device (200, 300). a portable main device with a first housing and a first mechanical connection assembly disposed on the first housing and a first electric connection assembly (120, 121) disposed on the first housing, and a portable additional device (200, 300), separate from the portable main device, with a second housing (240, 340) and a second mechanical connection assembly disposed on the second housing and a second electric connection assembly (220, 320) disposed on the second housing, wherein the portable main device can be mechanically connected to the portable additional device (200, 300) in a releasable manner by coupling the first mechanical connection assembly to the second mechanical connection assembly to form a structural unit, and wherein the portable main device can be electrically connected to the portable additional device (200, 300) via the first electric connection assembly (120, 121) and the second electric connection assembly (220, 320), characterized in that the portable main device has a power-amplifying device for generating a power signal which is to be transmitted to the portable additional device (200, 300) via the first electric connection assembly (120, 121) and the second electric connection assembly (220, 320), that the portable additional device (200, 300) has a test signal apparatus for generating a test signal, which is to be output to the electric device (30, 34), on the basis of the power signal of the portable main device, and that the portable main device has a measuring device for measuring a measurement variable of the electric device (30, 34) as a test response to the test signal of the portable additional device (200, 300).