xUnitnet

xUnit.net, commonly referred to as xUnit.net, is a free, open-source unit testing framework for .NET languages. It supports .NET Framework, .NET Core, and .NET 5+ applications, and runs on Windows, Linux, and macOS via the .NET runtime. It is designed as a modern alternative to other frameworks like NUnit and MSTest, emphasizing a simple attribute-based syntax and a test-driven development workflow. Tests are discovered and executed by test runners such as dotnet test, Visual Studio, or third-party runners.

Test methods are decorated with [Fact] for simple tests or [Theory] for data-driven tests. Theories use data attributes such as [InlineData], [MemberData], or [ClassData]. Each test runs in a separate instance of the test class by default, enabling isolation. Setup and teardown are handled via constructors and IDisposable, or through fixtures using IClassFixture and ICollectionFixture to share context across tests or test classes. The framework supports parallel test execution, configurable via attributes and config files, and allows skipping tests with a Skip property.

xUnit.net ships as NuGet packages: xunit for framework APIs, xunit.runner.visualstudio for Visual Studio integration, and xunit.runner.dotnet for dotnet test compatibility. It integrates with commonly used test runners and supports dependency injection in tests through custom fixtures. It has an active community and ecosystem of extensions and tools.