Testing evolving software

Regression testing, which attempts to validate modified software and ensure that no new errors are introduced into previously tested code, is used ext ensively during maintenance of evolving software. Despite efforts to reduce its cost, regression testing remains one of the most expensive activities performed during a software system's lifetime. Because regression testing i s important and expensive, many researchers have focused on ways to make it more efficient and effective. Research on regression testing spans a wide variety of topics, including test environments and automation, capture-play back mechanisms, regression-test selection, coverage identification, test s uite maintenance, regression testability, and regression-testing process. T his paper discusses the state of the art in several important aspects of re gression testing,and presents some promising areas for future research. (C) 1999 Elsevier Science Inc. All rights reserved.