Non-functional testing focuses on quality attributes, not features. It allows you to determine how well the software works.
It answers questions like:
- Is it fast?
- Is it reliable?
- Is it easy to use?
- Does it scale under load?
Examples include:
- Performance testing
- Usability testing
- Reliability testing
Simple rule:
- Functional testing = what the system does
- Non-functional testing = how well it does it