How do you organize test classes and test collections in xUnit?

Short answer: Group related tests in the same class. Use Collection attribute to group classes that share setup/teardown or should not run in parallel. [Collection("Database collection")] public class TestClass1 { } [Collection("Database collection")] public class TestClass2 { }

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.