Retesting software during development and maintenance

As most software continually evolves and changes during development and maintenance, it is necessary to test new and modified parts and retest existing parts that might have been affected by the changes. This activity is called regression testing and can account for a large percentage of the overall cost of software development. For this reason, much research has been (and is still being) performed on regression testing. This paper presents an overview of the major issues involved in software regression testing, an analysis of the state of the research and the state of the practice in regression testing in both academia and industry, and a discussion of the main open challenges for regression testing.