A memory device includes memory cell array and an address decoder. The memory cell array includes a normal memory region and a redundant memory region. The normal memory region operates in response to data signal and plurality of normal memory region signals. The redundant memory region operates in response to data signal and plurality of redundant memory region signals. The address decoder includes normal memory region signal generator and redundant memory region signal generator. The normal memory region signal generator activates first normal memory region signals and redundant memory region signal generator activates first redundant memory region signal simultaneously when address decoder operates in test mode. First normal memory region signals correspond to an address signal and are included in plurality of normal memory region signals. A first redundant memory region signal corresponds to an address signal and is included in the plurality of redundant memory region signals.