A test assembly includes multiple circuit boards. Each board includes multiple pairs of contacts configurable to address the respective circuit board, an instrument, first and second headers at opposing edges of the respective board. Each pin of a first header electrically connects through the board to a corresponding pin of a second header. Each board includes first and second input/output (I/O) terminals at opposing edges of the respective board, the first I/O terminal electrically connects through the board to the second I/O terminal. A relay on the board permits the board's instrument to be activated. Each of the circuit boards mechanically and electrically connects to another circuit board through a jumper cable connecting the first header of one circuit board to the second header of another circuit board and through a conductive member electrically connecting the first I/O terminal of one board to the second I/O terminal of another board.