Your question is Testing Hardware-Dependent Embedded Code. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
How do you write tests for code that interacts directly with hardware? Walk through how you would structure the code, what you would mock or fake, and how you would balance unit tests, simulator tests, and tests on real devices.