The present application discloses an apparatus for testing defects of a memory module comprises a central buffer for generating a test write command and a test read command to indicate testing to a target address in a memory module; and a data buffer coupled to the central buffer to receive the test write command and the test read command; the data buffer is configured to, in response to the test write command, use target data as repair data corresponding to the target address, and write the target data into the memory module; and, in response to the test read command, to read target data from the target address and compare the target data with the repair data, and to send to the central buffer a comparison result of the target data and the repair data; the central buffer is further configured to record the target address as a tested address when generating the test write command, and determine whether to add the tested address to defective address information based on the comparison result associated with the tested address, defective address information is to indicate one or more defective memory addresses in the memory module.