A new Mule application under development must implement extensive data transformation logic.

Explanation

Correct answer is Implement transformation logic in the new Mule application using DataWeave, invoking existing transformation services when possible. * The key here minimal testing effort, "Extend existing transformation logic" is not a feasible option because additional functionality is highly specific to the new Mule application so it should not be a part of commonly used functionality. So this option is ruled out. * "Implement transformation logic in the new Mule application using DataWeave, replicating the transformation logic of existing transformation services" Replicating the transformation logic of existing transformation services will cause duplicity of code. So this option is ruled out. * "Implement and expose all transformation logic as microservices using DataWeave, so it can be reused by any application component that needs it, including the new Mule application" as question specifies that the transformation is app specific and wont be used outside