What regression testing is
Regression testing is the practice of re-running tests after changes are made to software, to confirm that existing features still work correctly. A regression is when something that used to work stops working because of a change. Regression testing guards against this by checking that recent changes have not unintentionally broken previously working parts of the program.
The problem it solves
Whenever software is changed - to add a feature, fix a bug, or improve something - there is a risk that the change accidentally breaks something else that was working before. These unintended breakages can be easy to miss. Regression testing addresses this risk by re-testing existing functionality after changes, catching cases where a change has caused a previously working feature to fail.
How regression testing works
Regression testing works by re-running a set of existing tests after changes are made. These tests cover functionality that was already working, so if any of them now fail, it signals that the recent change broke something. Because the same tests are run again and again as the software evolves, regression testing is often automated so it can be done quickly and frequently.
Why it matters as software grows
As software grows and changes over time, the chance of accidentally breaking existing features increases. Regression testing becomes more important the more a program is modified, since each change is a new opportunity for a regression. By continually re-checking that old features still work, regression testing helps keep software stable even as it is actively developed and improved.
Regression testing and automation
Because regression testing involves repeatedly running the same tests, it is well suited to automation. Automated regression tests can be run every time the code changes, quickly flagging any newly broken functionality. This makes it practical to catch regressions immediately, rather than discovering them much later, and is a key reason automated testing is so valued in software development.
Why it matters
Regression testing is essential for keeping software reliable as it changes over time. Understanding what regression testing is - re-running tests to ensure changes have not broken existing features - clarifies how developers safely evolve software. For anyone interested in software quality, it is an important concept to understand.
Related on Skillo
See also: What is continuous integration (CI/CD)?, What is unit testing? Explained.
Sources
Published date reflects the original event date (2024-06-18). This article is original Skillo editorial written from the sources above; facts were verified in September 2026.
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