xunit.extensibility.execution by: James Newkirk, Brad Wilson

Includes xunit.execution.*.dll for extensibility purposes. Supports .NET 4.5.2 or later, and .NET Standard 1.1.

Xunit.StaFact by: Andrew Arnott

Make your xunit tests more closely emulate your application by running them on STA threads, with support for various SynchronizationContexts.