Quality Assurance (QA) is the systematic discipline of ensuring products and services meet defined quality standards through planned, preventive activities applied across the development lifecycle. Distinct from Quality Control, QA is process-oriented — encompassing both verification and validation to confirm that the right product is being built correctly. Practitioners integrate manual and automated testing methodologies, from unit and integration tests to exploratory and user acceptance testing, embedding quality gates into continuous integration pipelines. Key metrics include defect density, test coverage, mean time to detect, and escaped defect rate.
