Covers xUnit v3 testing patterns with migration notes for projects still on v2. You'll use this when writing Fact and Theory tests, setting up class and collection fixtures, or dealing with async lifecycle hooks that now return ValueTask instead of Task. The skill draws clear lines between v3's strongly typed TheoryDataRow and v2's object arrays, which matters during upgrades. It assumes your test project is already scaffolded and stays focused on xUnit mechanics rather than broader testing strategy. Good reference for parallelism configuration and the removal of assertion message parameters in v3.
npx skills add https://github.com/wshaddix/dotnet-skills --skill dotnet-xunit