In this paper we propose a low-cost board-level testing method for printed circuit boards in microprocessor-based systems. The fault detection is achieved by replacing the CPU with a bus emulator to test faults on wiring interconnects. Test patterns are sent by the bus emulator and the results are collected by it later for analysis. We also discuss how to derive minimum test sets for the diagnosis of all modeled faults. Multiple-board systems can be tested by hierarchically applying our method. With this approach, board testing is conducted in a way similar to functional testing while at the same time reach the controllability and observability offered by in-circuit testing.