Apparatus for diagnosing memory system and operating method thereof

A test device which is electrically coupled with at least one memory device in a memory system and engaged with, or included in, a controller handling an operation in the at least one memory device, the test device is configured to cause the memory system to:

• perform a write operation to a first region of the at least one memory device in response to a first write command set;
• output read data through reading the first region programmed in response to the first write command set;
• reorganize plural write command data regarding the first write command set based on the read data;
• arrange reorganized write command data based on an index of each reorganized write command data;
• generate estimated read data based on arranged write command data;
• and
• compare the read data with the estimated read data to verify an operation result of the first write command set.