How does xUnit differ from NUnit and MSTest?

Short answer: xUnit encourages constructor injection for setup instead of [SetUp] methods. It uses [Fact] and [Theory] attributes for test methods, while NUnit/MSTest use [Test] and [TestMethod]. xUnit does not use [TestInitialize]/[TestCleanup] but favors class fixtures and constructor/dispose patterns. xUnit is better integrated with .NET Core and supports parallel test execution by default.

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.