This repository contains Roslyn diagnostic analyzers and code fix providers for the xUnit.net test framework (v2 and v3, including Native AOT). It enforces best practices, detects common anti-patterns (e.g., misuse of Assert methods, serialization issues with theory data, incorrect async handling, and structural problems in test classes), and provides automated code fixes. The codebase is organized around version-aware context classes (XunitContext) that resolve xUnit types and version-specific behavior, allowing a single analyzer to target multiple xUnit versions. It includes a rich test suite using a custom CSharpVerifier base class, building on Microsoft.CodeAnalysis.Testing. The infrastructure is well-abstracted with reusable base classes for analyzers, suppressors, and fix providers, and the project is packaged as a NuGet package automatically referenced by xUnit projects.