Can you explain the concept of test fixtures in xUnit?

Short answer: Test fixtures provide a way to share setup and cleanup code between tests. xUnit supports: Class Fixtures: Shared across all tests in a class. Collection Fixtures: Shared across multiple test classes. They are implemented by creating a fixture class and injecting it into test classes via constructor.

Real-world example (ShopNest)

ShopNest unit tests cover pricing and discount rules so a bad coupon change fails in CI before customers see it.

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.