When should you test?
Rough drafts are the staple of the creative business. Art directors sketch and storyboard. Interaction designers mock and prototype.
How soon should you put it in front of people to get their feedback?
On the one hand, an IDEO designer says sooner rather than later:
Instead of starting with our usual process where we gather inspiration, we thought: What if we share a prototype we are really excited about with the client right away?
On the other hand, Alan Cooper cautions in a Twitter thread:
Prototyping and testing is not interaction design. It helps, but it isn’t user centered. It’s designer centered. Prototyping & testing has one huge virtue: it makes management happy because it never rocks the boat. It never requires big changes. It always keeps the designer in command. It’s very ego gratifying.
When you put an artifact in front of a user, you instantly shut down an infinity of good ideas, avenues of thought, opportunities to create.
In other words, the first prototype you show sets the direction for everything that follows. It becomes the reference point. Put the first button in the wrong hole, and you'll will mess up the rest.
This is something that should be considered a lot more often than it is in practice.