Xunit

XUnit is a term used to describe a family of unit testing frameworks that are modeled after JUnit and share a common design heritage from SUnit. The name is not a single product but a label for multiple implementations across programming languages. The first wave followed JUnit's success in the Java ecosystem, inspiring similar tools in other languages, each adapting the approach to its language's idioms and tooling.

Core idea: unit tests are code that exercise small units of functionality in isolation. A test defines inputs, invokes code under test, and asserts expected outcomes. Tests are collected by a test runner, executed, and reported as pass/fail. Common features include test discovery, fixtures for preparing test context, and an assertion library for verifying conditions. Many xUnit frameworks emphasize simple, repeatable tests that do not depend on external state.

Notable examples include JUnit for Java, PyUnit (unittest) for Python, NUnit for .NET, PHPUnit for PHP, and xUnit.net for .NET. While each language has its own conventions, xUnit-style frameworks typically provide attributes or annotations to mark tests, support for parameterized tests, and mechanisms for shared fixtures. In xUnit.net, for example, test methods are marked with [Fact] for simple tests or [Theory] with data attributes for parameterized tests; setup and teardown are implemented via constructors and IDisposable rather than dedicated attributes.

The xUnit family is widely used in continuous integration and test-driven development, aligning with modern practices such as automated test execution, isolation, and fast feedback loops.