An object-oriented automated testing system and method tests program subroutines which operate on parameter data objects to generate results. Tests determine whether the subroutines meet design specifications provided by test engineers in the form of precondition objects and postcondition objects. The precondition objects comprise data invariant objects and functional precondition objects and are applied to a generated pool of candidate parameter data objects to check data syntax and data semantics, respectively before the parameter data is applied to the subroutines. Each parameter data object belongs to a predetermined data type and the precondition objects are written for generic data types and associated with each parameter data object during the testing process. The subroutines are run with the checked data by an automatically generated test program. After the subroutines have been run the results are checked for proper syntax and semantics by the postconditions to determine whether design specifications have been met.