MEMORY DEVICE CAPABLE OF OUTPUTTING FAIL DATA IN PARALLEL BIT TEST AND MEMORY SYSTEM INCLUDING THE MEMORY DEVICE

A memory device includes a memory cell array and a test controller. The memory cell array includes a plurality of memory cells, where the memory cell array is divided into multiple regions. The test controller is configured to perform a parallel bit test (PBT) on the plurality of memory cells, where the test controller selects fail data including a fail data bit among internal data output from the multiple regions during the PBT, and outputs the fail data via a data input/output signal line to the outside of the memory device.