Engineers often customize design methods for specific problems and tasks, making it relatively straightforward to demonstrate internal correctness (verification). However, establishing the general applicability of these methods to a broader class of problems (validation) is more complicated. Key challenges include defining the scope and characteristics of the problem class, identifying modulable and adjustable functions, rules, mechanisms, and hyperparameters of the design method, and determining how to adapt the method for new and similar problems. In this chapter, we systematically address these questions, providing a framework for validating the proposed design evolution cycle and incorporated methods, and demonstrating their adaptability across various engineering design contexts and scenarios.