Introduction to Software Quality Assurance
Software Quality Assurance (QA) is the systematic process of evaluating whether software meets defined quality standards and requirements before it reaches users. It encompasses testing, process improvements, standards, and practices that collectively reduce defects and improve the reliability and usability of software products.
QA vs Testing
QA is broader than testing. Testing finds defects after code is written. QA aims to prevent defects from entering the code in the first place — through requirements clarity, process standards, design reviews, and building quality into the development process. Both are necessary: prevention is more efficient than detection, but testing remains essential to catch what prevention misses.
The Cost of Defects
Defects found in requirements cost approximately 1 unit to fix. The same defect found during design costs approximately 10 units, during testing 100 units, and in production 1,000 units. This widely-cited model (from IBM studies) has variability by context, but the directional point is robust: catching defects earlier is dramatically cheaper than catching them later.
Quality Dimensions
- Functional quality: Does the software do what it's supposed to do?
- Performance quality: Does it do it fast enough?
- Reliability quality: Does it do it consistently, without failures?
- Security quality: Is it resistant to exploitation?
- Usability quality: Can users accomplish their goals effectively and with satisfaction?