The Main Idea:

You and your team heavily test the prototype you made in the last phase to see if you're actually solving users' problems. This is the technically the last step in a linear 5-step model, but often times you'll uncover ways to solve new problems that result from this phase, and then test again.

Author/Copyright holder: Teo Yu Siang and Interaction Design Foundation. Copyright licence: CC BY-NC-SA 3.0