Preventing data errors with continuous testing

Today, software systems that rely on data are ubiquitous, and ensuring the data's quality is an increasingly important challenge as data errors result in annual multi-billion dollar losses. While software debugging and testing have received heavy research attention, less effort has been devoted to data debugging: identifying system errors caused by well-formed but incorrect data. We present continuous data testing (CDT), a low-overhead, delay-free technique that quickly identifies likely data errors. CDT continuously executes domain-specific test queries; when a test fails, CDT unobtrusively warns the user or administrator. We implement CDT in the ConTest prototype for the PostgreSQL database management system. A feasibility user study with 96 humans shows that ConTest was extremely effective in a setting with a data entry application at guarding against data errors: With ConTest, users corrected 98.4% of their errors, as opposed to 40.2% without, even when we injected 40% false positives into ConTest's output. Further, when using ConTest, users corrected data entry errors 3.2 times faster than when using state-of-the-art methods.