dotnet-testing-unit-test-fundamentals

The FIRST principles in .NET unit testing require tests to be Fast, Independent, Repeatable, Self-Validating, and Timely. Applying these concepts ensures your test suite remains maintainable and provides reliable code validation throughout development.

To write a unit test with xUnit, structure your code using the Arrange-Act-Assert pattern to set up data, execute the method, and verify results. Utilize `[Fact]` for single tests and `[Theory]` with `[InlineData]` for parameterized scenarios.

You test exceptions in .NET using xUnit by writing specific tests that verify expected exception throwing. This ensures your methods properly handle invalid inputs and error states by asserting that the correct exceptions are raised during execution.

The best naming conventions for xUnit test methods prioritize descriptive names that clearly communicate the tested scenario and expected outcome. Adopting clear test naming conventions improves maintainability and helps developers quickly understand test purposes.

Use `[Fact]` in xUnit testing for single, non-parameterized test scenarios, and use `[Theory]` combined with `[InlineData]` when you need to run the same test logic against multiple data sets for broader code coverage.