An aspect of the present invention is drawn to a system that includes an automatic test engine, a decompressor, a first scan chain, a second scan chain, a compactor and a debug output. The automatic test engine is operable to output a test output, to receive a resultant input, to receive a debug input, to monitor the debug input and to compare the test output with the resultant input. The decompressor is arranged to receive a decompressor input based on the test output, to output a decompressor output. The scan chains are arranged to receive input based on the decompressor output, and each scan chain includes at least one flip-flop. The compactor is arranged to receive input based output from the flip-flops, and to output a compactor output. The debug output line is arranged to receive the flip-flop output.