A method of testing a semiconductor memory device includes writing first data to a memory cell array in the semiconductor memory device, loading second data from the memory cell array onto a plurality of data pads of the semiconductor memory device, rewriting the second data to the memory cell array, and outputting test result data through one or more test pads. The first data is received from an external device through the one or more test pads, which correspond to one or more of the plurality of data pads. The test result data is based on the rewritten data in the memory cell array.