Performance Testing
Performance testing measures how a system responds under a given workload — speed, stability, resource usage — covering the broader category that load, stress, spike, and soak testing are all specific types of. It exists to answer "how does this behave under realistic and extreme conditions," not just "does it work."
Performance testing is a non-functional testing discipline: it assumes the system already works correctly and asks a different question entirely — does it work correctly fast enough, at the scale needed, without falling over. A feature can pass every functional test and still be a performance failure if it takes ten seconds to respond under real traffic.
Each performance testing subtype targets a different question: load testing checks expected traffic, stress testing checks the breaking point, spike testing checks sudden traffic surges, and soak testing checks long-duration stability — together giving a much fuller picture than any single test type alone.
