A test system includes a non-volatile memory device that includes a plurality of memory blocks operating in a multi-plane mode, and a test machine that detects a bad block of the non-volatile memory device. The non-volatile memory device generates a ready/busy signal which is based on whether an erase loop for detection of the bad block progresses. When at least one normal block is detected from the plurality of memory blocks included in planes operating in the multi-plane mode, the non-volatile memory device generates the ready/busy signal having a first busy interval. When all the memory blocks included in the planes operating in the multi-plane mode are detected as bad blocks, the non-volatile memory device generates the ready/busy signal having a second busy interval shorter than the first busy interval.