What are the advantages of using DI in unit testing?

Short answer: Easier mocking of dependencies using frameworks like Moq or NSubstitute. No need to instantiate real implementations (e.g., database access) for tests. Improved isolation of the unit under test. Faster, more reliable tests due to lack of external dependency reliance.

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.