The design process of a product has the following phases. Although it is good to have a clear idea of the design process it is important to remember that unlike the figure below the design process is much more messy, complicated and spiral than portrayed.
One of my favorite models of iterative design from the book ‘Game Design Workshop’ is provided below. It is less detailed but captures the feel of the process better. An ideal process model would be a combination of these models.
Thinking about People (Ch-1) in Kolko, J. (2011). Thoughts on Interaction Design (2nd ed.) Burlington, MA: Morgan Kaufmann (pg. 20 – 39)
Playtesting (Ch-9) in Fullerton, T. (2014). Game design workshop: a playcentric approach to creating innovative games. CRC press.