In which scenario would a developer use endurance testing?

Endurance testing is specifically designed to assess the long-term stability of an application. This type of testing involves running a system under a significant load for an extended period to identify any performance degradation, memory leaks, or issues that may not surface during shorter performance tests. By simulating prolonged usage, developers can ensure that the application maintains its efficiency, responsiveness, and overall stability when subjected to continuous demands.

In contrast, the other scenarios touch upon different testing purposes. Evaluating system capacity under peak load focuses on stress testing, ensuring an application can handle high traffic in short bursts. Ensuring feature functionality relates to functional testing, verifying that each feature works as intended. Analyzing data retrieval speed aligns more closely with performance testing, which gauges how quickly data can be fetched. Therefore, the scenario that accurately depicts the purpose of endurance testing is the assessment of the application's long-term stability.