From a testing perspective, it makes no difference how a programmatic solution is implemented if the functionality remains the same. What matters is how the system behaves, and not what goes into that behaviour.
Functional testing ought to treat the system as a black box. This decouples the testing suite from the solution, allowing testers to focus on the quality of the software rather than getting bogged down in the details of how the software works.
This also gives the programmers the freedom to refactor the solution without causing extra rework on the testing suite.
The question, always, is what value does it provide? The cost of testing the programmatic details not only has the time expense of the testing, but the additional cost of not focusing that effort elsewhere.