Abstract: A method determines if a revised fragment of a program provides an identical answer as does an original fragment of the program, wherein a fragment is one operator and one or more operands that are subject to processing by the operator. The method comprises the steps of: executing both an original fragment of the program and one or more revised fragment(s) which correspond to the original fragment, using first equvalent variables and determining if both fragments produce equivalent results; executing both the revised fragment(s) and the original fragment of the program using additional variables to determine if both fragments produce equivalent results under all test conditions; if the results are not equivalent, making a notation of that fact for later examination; and if the fragments are equivalent, repeating the aforementioned test steps until all revised code fragments have been tested.