Which type of performance test assesses how much load a system can handle before performance is impacted?

Stress testing is designed to evaluate how a system behaves under extreme conditions, specifically to determine the limits of functionality. By gradually increasing the load on the system to a breaking point, stress testing helps in identifying the maximum capacity the system can handle before performance degrades. This testing is crucial because it not only uncovers the breaking points of a system but also provides insight into how the system manages resources, error handling, and recovery when subjected to heavy workloads.

The focus of stress testing is on identifying weaknesses and potential points of failure under excessive load, which could ultimately lead to service disruptions. This information is vital for performance tuning and ensuring that the system can withstand unexpected high-volume scenarios in real-world operations. In contrast, other types of testing such as endurance, volume, and scalability testing have different primary focuses, which do not directly address the goal of pushing a system to its limits to observe performance degradation.