A method for the test of VLSI chips and high-density PC boards is proposed. A built-in, microprogrammable test controller, called a testprocessor, applied tests to all separately testable blocks within either a VLSI chip or PC board, hence increasing controllability and observability. Facilities for test-pattern storage and test-result evaluation as well as means for test-pattern generation and response compaction are provided; consequently, most tasks commonly associated with an external test equipment can be covered by the testprocessor. In contrast to most concepts of built-in test known to date, the testprocessor support tests of all kinds (structural, functional, pseudorandom), applied serially or in parallel; furthermore, adaptation to standardized test interfaces can easily be achieved. The concept is intended to simplify wafer test, production test, and testing burn-in, and it supports field maintenance and system self-test. >