While people often use the terms “testing” and “quality assurance” (QA) interchangeably, testing and QA are not the same. Testing is a form of quality control (QC). QC is a product-oriented, corrective approach that focuses on those activities supporting the achievement of appropriate levels of quality. Testing is a major form of quality control, while others include formal methods (model checking and proof of correctness), simulation and prototyping.
QA is a process-oriented, preventive approach that focuses on the implementation and improvement of processes. It works on the basis that if a good process is followed correctly, then it will generate a good
product. QA applies to both the development and testing processes, and is the responsibility of everyone on a project.
Test results are used by QA and QC. In QC they are used to fix defects, while in QA they provide feedback on how well the development and test processes are performing.