Priority based data flow testing

Software testing is an expensive component of software development and maintenance. For data flow testing, test cases must be found to test the def-use pairs in a program. Since some of the def-use pairs identified through static analysis may be infeasible, no amount of testing effort may result in exhaustive testing of a program. Therefore in practice a fixed amount of effort is spent in testing a program. We develop an approach for assigning priorities to def-use pairs, such that the def-use pairs with higher priorities can be expected to require less effort for test case generation and therefore testing. Thus, by using the priorities as a guide for ordering the def-use pairs for testing, we can maximize the number of def-use pairs tested using a fixed amount of testing effort. We apply the technique to regression testing during the software maintenance phase, in which case the priorities are assigned to capture not only the difficulty in test case generation but also the likelihood that an error introduced by a program change is uncovered by the test case.