gistfile1.cs

using System;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using Microsoft.Practices.ServiceLocation;
using Moq;

namespace ServiceLocatorMocking
{
    [TestClass]
    public class UnitTest1
    {
        [TestMethod]
        public void TestMethod1()
        {
            ServiceLocatorConfig.AddItem<int>(4);

            Assert.AreEqual(4, ServiceLocator.Current.GetInstance<int>());
            
        }

        [TestMethod]
        public void TestMethod2()
        {
            ServiceLocatorConfig.AddItem<double>(3.3);

            Assert.AreEqual(3.3, ServiceLocator.Current.GetInstance<double>());
        }    

    }

    public class ServiceLocatorConfig
    {
        private static Mock<IServiceLocator> ServiceLocatorImpl { get; set; }

        static ServiceLocatorConfig()
        {
            ServiceLocatorImpl = new Mock<IServiceLocator>();

            ServiceLocator.SetLocatorProvider(() => ServiceLocatorImpl.Object);
        }
        
        public static void AddItem<T>(T objectToReturn)
        {        
            ServiceLocatorImpl.Setup(s => s.GetInstance<T>()).Returns(objectToReturn);
        }
    }

    

}