A method and apparatus for analog testing of hot-plug circuits on an active computer backplane. A test connector is added to the computer backplane that enables an external tester to turn on each card slot present on the computer backplane. The external tester then directs a test adapter card residing in a selected card slot to apply a nominal and overcurrent load to each voltage level of the selected card slot. After each load has been applied, the corresponding voltage level is returned to the external tester. The external tester then measures the voltage level, and verifies that the voltage level falls within a predefined voltage range. The test connector uses existing unutilized bus signal lines to pass test directives and results between the card slot under test and the external tester. The same test adapter card that performs the analog test on a card slot is also used to perform digital testing on the card, thus reducing both testing time and the complexity of the testing apparatus.