Can't add ReactiveUI to a NUnit Test Project

I am currently trying to setup Unit to unittest our ReactiveUI ViewModels using NUnit and Moq. However I can't get it working. I can't add ReactiveUI to a NUnit test library (Unable to resolve dependency 'Rx-Xaml (≥ 2.2.5)'), and I can't add Moq to a PCL project.

Is it even possible to unittest ReactiveUI ViewModels with NUnit and Moq?