Abstract: Apparatus for testing wiring harnesses either during or after the harness fabrication process comprises test points, each of which is connected to a corresponding terminal of the harness. Associated with the test points are a current source, a current sourcing means, a current sink, and a current sinking means. Each current sourcing means and current sinking means comprises a controlled conduction path which is selectively operable to a conductive state or a non-conductive state. The tester operates to test individual circuits of the harness for continuity and shorts. In doing this the controlling conduction paths are selectively operated in accordance with information correlating the wiring harness circuits with the test points. A current sensing means senses the present or absence of current during open and short circuit tests and provides appropriate indicator signals to indicate opens or shorts if such faults are present.