State Interface (ITrafficLightState):?

Short answer: The ITrafficLightState interface defines a method (Change) that allows the state to transition to another state. The method accepts a TrafficLight object as a parameter to facilitate the state change. public interface ITrafficLightState { void Change(TrafficLight light); } Each concrete state class (Red, Green, Yellow) will implement this interface, defining the specific behavior of the traffic light for that state.

Real-world example (ShopNest)

Use a GoF pattern in ShopNest only when it removes duplication or makes a change safer—explain the problem it solves in the interview.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.