dotnet-xunit

xUnit v3 testing framework features for .NET. Covers [Fact] and [Theory] attributes, test fixtures (IClassFixture, ICollectionFixture), parallel execution configuration, IAsyncLifetime 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.

Scope

• [Fact] and [Theory] test attributes and data sources
• Test fixtures (IClassFixture, ICollectionFixture) and shared context
• Parallel execution configuration and collection ordering
• IAsyncLifetime for async setup/teardown
• xUnit analyzers and custom assertions
• xUnit v3 migration from v2 (TheoryDataRow, ValueTask lifecycle)

Out of scope