Requirements: Create a working prototype of the thing you are testing. It must at least cover the main functionality and look and feel like the real thing.
UX Test Results: Users did not use additional functionality buttons (e.g. "reheat") unless prompted. When asked, mentioned at least half of them could be removed with no loss in experience.
Design Implications: Remove extraneous features. Work to make buttons more discoverable. Rework prototype to feel more realistic.