Clean Unit Testing in .NET: Practical xUnit and Moq Tips

When writing unit tests in .NET, the basics are easy to learn. Frameworks like xUnit and Moq make it straightforward to create tests, mock dependencies and verify behavior. The real challenges appear later, when you start testing real production code. Sooner or later, you run into practical questions that documentation rarely answers clearly: What is the cleanest way to configure IOptions<T> in unit tests? How can you test internal classes without making them public? How do you verify ILogger calls using Moq without verbose boilerplate? How can you test ILogger calls without Moq at all? How do you log output in xUnit tests? How can you keep [Theory] tests type-safe? How can you assert objects created internally using Moq .Callback? These are not complex architectural problems, just practical issues that appear repeatedly in real projects. This article shows practical unit testing tips and tricks for .NET developers, helping you write cleaner, more maintainable tests with xUnit an