A testing device includes a measuring unit, a testing board supporting the measuring unit and connected to the measuring unit, and a connecting interface coupled to the testing board. The connecting interface includes connecting terminals protruding in a direction away from the testing board, and is connected to a device under test (DUT) via the connecting terminals. When the DUT is connected to the connecting interface, the measuring unit supplies a constant electric current via the testing board and the connecting interface to the DUT for a preset duration to result in a voltage, measures the voltage, and determines, based on a result of measurement of the voltage, an electrical connection status of the DUT.