Make Tests project run with Xamarin Studio

This line:

<ProjectTypeGuids>{3AC096D0-A1C2-E12C-1390-A8335801FDAB};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>

in the .csproj file was preventing the Tests from running with Xamarin Studio
as it was flagging the project as a MSTest type.
Xamarin Studio user preferences