Abstract: A system for testing a hardware unit containing sensitive information, while inhibiting access to that information, includes a secure program in an Automated Test Station and an interface circuit. The test station has a programmed processor, as well as generating equipment which generates pseudo test signals and measuring devices which measure the response of the unit to actual test signals. Within the processor of the test station there is a test program which does not indicate the sensitive information and a run-time program that interprets the test-program to generate encoded commands for carrying out the test. The interface circuit receives the encoded commands and the pseudo test signals from the test station, decodes the encoded commands and generates the actual test signals. These actual test signals are routed to the unit under test by the interface circuit.