Abstract: An address and data bus connects a multiplicity of ports into which test modules can be inserted with a microcomputer controlled by a keyboard for performing tests on circuit boards or other electronic units through test plugs that are interconnected with the data ports where the test modules are plugged in. When the test system is put into operation, all of the ports of the data bus are addressed to produce an indication of which ports are occupied by test modules as well as of the nature of the test modules. When it is desired to produce a test, each step of the procedure is performed by operation of a keyboard with reference to available options presented on the computer display on the basis of the configuration of test modules that have been plugged in. Coupling fields are interposed between data ports designed to receive test modules utilizing analog circuits and a test connector for connection to equipment under test.