Certified Associate in Software Testing (CAST) Practice Test

The method that involves running an old system alongside a new one to compare results is known as Parallel Testing. This approach is particularly useful when transitioning from a legacy system to a new one, as it allows testers to verify that both systems produce the same outputs under similar conditions. By executing the same processes on both systems simultaneously, testers can identify any discrepancies and ensure that the new system is functioning as intended before fully replacing the old one.

This method is critical because it provides a safety net during a transition, ensuring that data integrity and system functionality are maintained, which is essential for reducing risk during deployment. It also allows for a direct comparison of outcomes, helping stakeholders make informed decisions about the readiness of the new system.

The other methods, while important in their own contexts, do not specifically refer to running both systems side by side for comparative analysis. System Testing focuses on verifying that the entire system meets specified requirements, Validation Testing checks that the product meets business needs and expectations, and Performance Testing assesses how well a system performs under certain conditions but does not focus on comparison with another system.