Regression Testing

Regression testing involves testing unrelated functionality on a site after making a change elsewhere in order to confirm your new change didn't break anything that was previously working.

Sites are interconnected, and a fix in one place can have surprising effects somewhere else — for example, if you patch the contact form and somehow the search box stops returning results. Regression testing guards against this. It's a core part of quality assurance, and it matters most during ongoing maintenance, when developers ship updates to a live site. Many teams automate it so the same checks run on every deployment.