Which testing type assesses system performance under specific conditions, including heavy load?

The correct choice focuses on Performance Testing as the type that assesses system performance under specific conditions, particularly during heavy load scenarios. Performance Testing encompasses a broad range of methodologies aimed at evaluating various parameters of a system, including responsiveness, throughput, and resource utilization when subjected to different types of demands.

Load Testing, while it specifically examines how the system behaves under anticipated peak load, falls under the umbrella of Performance Testing. Performance Testing is the overarching category that includes load, stress, and other specific types of evaluations to understand how a system performs in a range of operational scenarios, especially under heavy or sustained load conditions.

In contrast, Regression Testing is primarily concerned with verifying that changes in code, such as bug fixes or new features, do not adversely affect existing functionality. White Box Testing focuses on the internal structures or workings of an application, allowing for testing based on the internal logic of the code rather than the overall system performance in varied conditions.

Thus, Performance Testing is the most appropriate choice for evaluating a system's performance under specific circumstances, including heavy loads.