How to test repository or data access layer?

Short answer: Mocking DbContext using frameworks like Moq (complex). Use InMemoryDatabase provider from EF Core for integration-like tests. Abstract dependencies and inject mocked interfaces for isolation. Performance, Best Practices, & Advanced Features

Real-world example (ShopNest)

ShopNest registers AppDbContext as scoped. One HTTP request = one context. Never inject it as a singleton.

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.