The first public beta of xUnit support for Xamarin is now available. Runner apps can execute the tests, much like they do currently with NUnitLite.
To get started, create a new blank application and add a reference to the xUnit.Runner.Xamarin package. The package contains a sample AppDelegate/MainActivity to get started.
Your tests can be in either the same project as the App Runner or it can be in referenced libraries, including PCL test assemblies. If your tests are in another assembly, simply add that assembly to the list of assemblies that contain tests (see the AppDelegate/MainActivity).
Please msg me on twitter @onovotny, if you have questions.
Then just run your app to execute tests. Tests