ISTQB Performance Testing Glossary

About this topic

Source: ISTQB Certified Tester Performance Testing (CT-PT)

Performance testing measures how a system behaves under a given workload — how fast it responds, how much it can handle, and what happens when you push past that. These terms come from the ISTQB Performance Testing syllabus; Foundation Level covers performance only as a non-functional test type.

The distinct test types are routinely confused, and the distinction is about what varies. Load testing evaluates behaviour under expected load. Stress testing pushes beyond expected load to find the breaking point and observe how the system degrades. Spike testing applies a sudden sharp increase. Endurance testing sustains a normal load over a long period to expose problems such as memory leaks that only surface with time. Scalability testing measures the system's ability to handle growth, and capacity testing establishes the maximum it can support while still meeting its requirements.

Workload is modelled through an operational profile — a description of how real users actually distribute their activity — which is then realised as a load profile with virtual users, ramp-up, and ramp-down phases. A test whose profile does not resemble reality produces numbers that mean nothing, which is the most common way performance testing goes wrong.

Results are read against ISO 25010's performance efficiency characteristic and its sub-characteristics: time behaviour (response times and throughput), resource utilisation (CPU, memory, network, storage), and capacity. System throughput is the volume processed per unit of time, and is often the metric stakeholders actually care about even when the conversation starts with response time.

What this topic covers

• Load, stress and spike testing
• Endurance and scalability testing
• Operational and load profiles
• Virtual users, ramp-up and ramp-down
• Throughput and time behaviour
• Resource utilisation