CAPM Practice: Validate requirements through product delivery

Regression testing confirms that new changes don't break previously validated requirements. Without regression testing, each new feature delivery could potentially invalidate requirements that were already successfully validated — a critical risk in iterative delivery.

**Why not B:** Testing performed at the end of a project to validate all requirements simultaneously describes final acceptance testing, not regression testing. Regression testing is specifically about re-testing previously validated functionality after changes are made, and it occurs throughout the project lifecycle, not just at the end.

**Why not C:** Measuring how quickly testers find defects over the project lifecycle describes a defect detection rate metric, not regression testing. Regression testing is about confirming that existing functionality remains intact after new changes, not about measuring tester productivity or defect discovery speed.

**Why not D:** Reviewing past project decisions for lessons learned describes a retrospective or lessons learned activity. Regression testing is a forward-looking quality assurance practice that verifies working features are not broken by new code changes, not a backward-looking review of decisions.