A testing device including a housing having an indicator, a first test probe configured to be inserted into an alternating-current (AC) receptacle, a second test probe configured to be inserted into a universal serial bus (USB) receptacle, a first test circuit located within the housing, and a second test circuit located within the housing. The first test circuit is coupled to the first test probe and is configured to receive an AC voltage from the AC receptacle, perform a first test on the AC voltage, and output a first signal to the indicator based on the first test. The second test circuit is electrically coupled to the second test probe and is configured to receive a USB voltage from the USB receptacle, perform a second test on the USB voltage, and output a second signal to the indicator base on the second test.