Abstract: A new structure of a test apparatus (tester) for detecting shorts and opens of a printed wiring board and an associated automatic test method. The tester has means for injecting signals into conductors of a printed wiring board under test (BUT) and a large number of integrated solenoid-actuated probes which are arranged in a two-dimensional array for sampling signals from the conductors of the BUT. The signals are sampled from the conductors by the integrated solenoid-actuated probes in a row by row scanning sequence following a grid pattern of the BUT. Each of the probes needs only to sample signals from the conductors in a small portion of the BUT.