dotnet-xunit xUnit v3 testing framework features for .NET. Covers and attributes, test fixtures ( , ), parallel execution configuration, for async setup/teardown, custom assertions, and xUnit analyzers. Includes v2 compatibility notes where behavior differs. Version assumptions: xUnit v3 primary (.NET 8.0+ baseline). Where v3 behavior differs from v2, compatibility notes are provided inline. xUnit v2 remains widely used; many projects will encounter both versions during migration. Out of scope: Test project scaffolding (creating xUnit projects, package references, Directory.Build.props) is ow…