Abstract: A portable circuit tester is disclosed which features efficient and simplified testing and fault identification of electronic units, such as circuit cards or the like. The tester incorporates an executive test program stored in a programmable read-only Memory (PROM) and accepts programmable test information related to individual units under test from PROM cards. The combination of the executive test program and a PROM card automatically applies test patterns to the unit under test and which patterns perform a go/no go acceptance test or a fault isolation test as may be desired.