A study of integration testing and software regression at the integration level

The authors identify the common errors and faults in combining modules into a working unit. They also make practical recommendations on test selection for integration testing and utilize these recommendations for regression testing at the integration level. With emphasis on reusing the previous test cases and retesting only the parts that are modified, one can reduce the testing expenses. The concept of `firewall´ is proposed to assist the tester in focusing on that part of the system where new errors may have been introduced by a correction or a design change. An experiment is presented in which an application of strategy is compared with the `retest-all´ strategy. By applying the approach for test selection, it is possible to discover all errors found by the retest-all strategy by executing only 35% of the total number of test cases