WiX Votive Managed Custom Action cannot be referenced by other managed code in the same solution?

Question

Question:

Is it possible to reference public static methods held within the CustomAction class, Votive generates for creating C# managed Custom Actions, from other libraries within the same solution?

I'm having trouble getting a reference to the class and method inside my C# library for the C# Custom Action when trying to create a test bed for the CA.

namespace TestInstaller.InstallCA
{
    public class CustomActions
    {
         [CustomAction]
         public static ActionResult InstallUIStart(Session session)
         {
             //Stuff
             return Begin(<Constructed DataClass>);                
         }

         public static ActionResult Begin(DataClass dc)
         {
             //Stuff I want to test
         }
    }
}

...

namespace TestInstaller.InstallerTest
{
    static class Program
    {
        Static void Main()
        {
            //Stuff
            //This line is not valid.
            TestInstaller.InstallCA.CustomActions.Begin(<Constructed DataClass>);
        }
    }
}

Despite me adding a reference to InstallCA I cannot add a using statement for TestInstaller.InstallCA or InstallCA, and the compile time error only suggests adding a reference, which I have done.

Is this anything to do with Votive protecting its DLLs somehow?