Final answer:
Parallel Testing is the approach where old and new systems are operated simultaneously in all locations to compare their outputs and confirm the new system works correctly before full deployment.
Step-by-step explanation:
The test approach where old and new systems operate simultaneously in all locations is known as Parallel Testing. This method is employed to verify that the new system behaves as expected by running it alongside the old system and comparing the results. For example, in a financial setting, both the existing and new accounting software would run at the same time, processing the same set of financial transactions to ensure that both systems produce the same outputs.
Parallel Testing differs from other testing methods because it involves running two versions of the software at the same time, rather than sequentially or in isolation. Unlike Regression Testing, which checks for new bugs in existing areas of a system after changes have been made, or Integration Testing, which verifies that software modules or subsystems work together, Parallel Testing focuses specifically on validating that a new system replicates the old system's functionality before it is fully deployed.
Furthermore, while System Testing is a broad testing phase that evaluates the complete and integrated software product to ensure compliance with the specified requirements, Parallel Testing is just one part of this larger umbrella of testing methodologies.