A system and associated method for building a datastore for storing and retrieving regression testing data for a complex application. The datastore receives a first input data, a first output data, a second input data, and a second output data. The datastore compares first input data to the second input data, modifying the first input data for use regression testing the complex application. The modified first input data is next used to regression test the complex application. The datastore receives the modified first output data from the complex application, comparing the modified first output data to the second output data. The datastore identifies discrepancies between the modified first output data and the second output data and sends a list of the discrepancies to an Application Expert.