Which testing type would you use primarily under extreme load conditions?

Stress testing is primarily used to determine the capabilities of a system under extreme load conditions. This type of testing pushes the system to its limits to see how it behaves under high levels of demand or stress. It helps identify the breaking point of the application and ensures that it can handle unexpected spikes in user activity or data input without failing.

Stress testing is essential for understanding how the system performs under conditions that are beyond normal or peak operational capacity. It helps uncover potential bottlenecks, memory leaks, and performance degradation that might not be visible under regular load tests. By simulating extreme conditions, stakeholders can ensure that the application is resilient and can maintain its performance, reliability, and stability even when faced with overwhelming demand.

Endurance testing, while related, focuses on evaluating the system's performance over an extended period under normal or moderate load, rather than extreme conditions. Load testing, meanwhile, assesses the system's performance at expected usage levels, ensuring it can handle anticipated traffic. Usability testing is concerned with the user interface and the overall user experience and does not focus on system performance under extreme load. Thus, stress testing is the most appropriate type of testing in this context.