The Double Diamond Framework clearly conveys a design process to designers and non-designers alike. The two diamonds represent a process of exploring an issue more widely or deeply (divergent thinking) and then taking focused action (convergent thinking).
This is not a linear process as the arrows on the diagram show. Teams often learn something more about the underlying problems which can send them back to the beginning. Making and testing very early-stage ideas can be part of discovery (low or high-fidelity prototyping).
If possible, experimentation with actual code to a limited set of users can provide invaluable feedback to how actual clients interact with the delivered code as validation of the concept. Tools such as FullStory can provide the usage data which can inform a new challenge to iterate on.