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Performance Testing: What It Measures, and How It Differs from Functional Testing
Performance testing puts numbers on a system under real or peak load – speed, capacity, throughput, how steady it stays. In commissioning it gets confused with functional testing, which only asks whether each function works at all. Performance testing asks how well, and against a target you have to hit.
What does performance testing measure?
It turns behavior into numbers. Usually:
- Throughput – units, volume or flow against the rated figure.
- Speed – how fast the system finishes its work under load.
- Capacity – the most it can sustain before output or quality drops.
- Stability – whether the numbers hold over a long run, not just a burst.
- Efficiency – energy or material used per unit made.
Performance or functional testing – what’s the difference?
Degree versus existence. Functional testing confirms a function works. Performance testing measures how well, against a target. A conveyor can pass functional testing by running both directions, then fail performance testing because it can’t hold the rated line speed. Functions get proven first; the numbers only mean something once they do.
When does performance testing happen?
Late in commissioning, after functions pass, and often inside the site acceptance test. Hitting the performance targets is usually the last piece of evidence needed for operational readiness and handover.
Performance vs functional testing at a glance
The same pair, read from the performance side.
| Aspect | Performance Testing | Functional Testing |
|---|---|---|
| Question | How well does it perform? | Does the function work? |
| Measures | Speed, capacity, throughput, stability | Correct behavior |
| Order | After functions pass | First |
| Passes when | It hits the target under load | It meets the spec |
| Example | Conveyor holds rated line speed | Conveyor runs both directions |
Free Performance Target Tracker
It lists each metric, its contract target and the measured result, so no system is accepted at 90 percent of rated output. Download the checklist (PDF). You can also complete the checklist digitally in flowdit on your phone, tablet or PC.
Related Terms
- Commissioning Process – the sequence this closes out.
- Factory Acceptance Test (FAT) – may fold in performance checks.
- Pre-Commissioning – the cold checks before any testing.
- Machine Availability – a live metric after start-up.
- Overall Equipment Effectiveness – rolls performance in with availability and quality.
Further Reading
- Commissioning-Software – commissioning end to end
