dotnet-xunit

SKILL.md

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.

Out of scope: Test project scaffolding (creating xUnit projects, package references, Directory.Build.props) is owned by [skill:dotnet-add-testing]. Testing strategy and test type decisions are covered by [skill:dotnet-testing-strategy]. Integration testing patterns (WebApplicationFactory, Testcontainers) are covered by [skill:dotnet-integration-testing].

Prerequisites: Test project already scaffolded via [skill:dotnet-add-testing] with xUnit packages referenced. Run [skill:dotnet-version-detection] to confirm .NET 8.0+ baseline for xUnit v3 support.

Cross-references: [skill:dotnet-testing-strategy] for deciding what to test and how, [skill:dotnet-integration-testing] for combining xUnit with WebApplicationFactory and Testcontainers.

xUnit v3 vs v2: Key Changes