Moq code for this SO question : http://stackoverflow.com/questions/21871678/mocking-with-moq-trying-to-pass-an-object-to-constructor-having-multiple-parame

gistfile1.cs

using System;
using System.Collections.Generic;
using System.Linq;
using Moq;
using NUnit.Framework;

namespace WindowsFormsApplication3
{
   public class CacheKeys
   {
      public const string ALLCODES = "ALL";
   }

   public interface ICacheManager
   {
      T Get<T>(string s);
      void Set(string s, object o, int timeOut);
   }
   public interface ISessionManager
   {
   }
   public interface IApplicationSettings
   {
      int CacheTimeout { get; set; }
   }
   public class EFDbContext
   {
      public virtual IEnumerable<SomeCodes> SomeCodes
      {
         get
         {
            throw new NotImplementedException(); // We're going to mock this anyway 
         }
      }
   }
   public class SomeCodes
   {
      public int Id;
      public string Code;
      public string Description;
   }

   public class CurrencyCodes : SomeCodes
   {
   }

   public interface ICodeService
   {
   }

   //CodeService.cs
   public class CodeService : ICodeService
   {
      private EFDbContext db;
      private ICacheManager cacheManager;
      private ISessionManager sessionManager;
      private IApplicationSettings appSettings;

      public CodeService(EFDbContext dbContext, ICacheManager cacheManager, ISessionManager sessionManager, IApplicationSettings appSettings)
      {
         db = dbContext;
         this.cacheManager = cacheManager;
         this.sessionManager = sessionManager;
         this.appSettings = appSettings;
      }

      public IEnumerable<SomeCodes> GetAllCodes()
      {
         var allCodes = cacheManager.Get<IEnumerable<SomeCodes>>(CacheKeys.ALLCODES);
         if (allCodes == null)
         {
            allCodes = db.SomeCodes.ToList();

            cacheManager.Set(CacheKeys.ALLCODES, allCodes, appSettings.CacheTimeout);
         }
         return allCodes;
      }

   }

   [TestFixture]
   public class MyTestClass
   {
      [Test]
      public void testCacheMiss()
      {
         var currencycodes = new List<SomeCodes>
         {
            new CurrencyCodes{Id = 1, Code = "IND", Description = "India"},
            new CurrencyCodes{Id = 2, Code = "USA", Description = "UnitedStates"},
            new CurrencyCodes{Id = 3, Code = "UAE", Description = "ArabEmirates"}
         };
         var mockEfContext = new Mock<EFDbContext>();
         var mockCacheManager = new Mock<ICacheManager>();
         var mockSessionManager = new Mock<ISessionManager>();
         var mockAppSettings = new Mock<IApplicationSettings>();

         // Setups for relevant methods of the above here, e.g. to test a cache miss
         mockEfContext.SetupGet(x => x.SomeCodes)
            .Returns(currencycodes); // Canned currencies
         mockCacheManager.Setup(x => x.Get<IEnumerable<SomeCodes>>(It.IsAny<string>()))
            .Returns<IEnumerable<SomeCodes>>(null); // Cache miss

         // Act
         var service = new CodeService(mockEfContext.Object, mockCacheManager.Object,
            mockSessionManager.Object, mockAppSettings.Object);
         var codes = service.GetAllCodes();

         // Assert + Verify
         mockCacheManager.Verify(x => x.Get<IEnumerable<SomeCodes>>(
            It.IsAny<string>()), Times.Once, "Must always check cache first");
         mockEfContext.VerifyGet(x => x.SomeCodes,
            Times.Once, "Because of the simulated cache miss, must go to the Db");
         Assert.AreEqual(currencycodes.Count, codes.Count(), "Must return the codes as-is");
      }

      [Test]
      public void testCacheHit()
      {
         // TODO refactor this into an object mother
         var currencycodes = new List<SomeCodes>
         {
            new CurrencyCodes{Id = 1, Code = "IND", Description = "India"},
            new CurrencyCodes{Id = 2, Code = "USA", Description = "UnitedStates"},
            new CurrencyCodes{Id = 3, Code = "UAE", Description = "ArabEmirates"}
         };

         var mockEfContext = new Mock<EFDbContext>();
         var mockCacheManager = new Mock<ICacheManager>();
         var mockSessionManager = new Mock<ISessionManager>();
         var mockAppSettings = new Mock<IApplicationSettings>();

         mockEfContext.SetupGet(x => x.SomeCodes)
                      .Throws(new Exception("mustnt hit the DB at all"));
         mockCacheManager.Setup(x => x.Get<IEnumerable<SomeCodes>>(It.Is<string>(s => s == CacheKeys.ALLCODES)))
            .Returns(currencycodes); // Cache miss

         // Act
         var service = new CodeService(mockEfContext.Object, mockCacheManager.Object,
             mockSessionManager.Object, mockAppSettings.Object);
         var codes = service.GetAllCodes();

         // Assert + Verify
         mockCacheManager.Verify(x => x.Get<IEnumerable<SomeCodes>>(
         It.Is<string>(s => s == CacheKeys.ALLCODES)), Times.Once, "Must always check cache first");
         mockEfContext.VerifyGet(x => x.SomeCodes, Times.Never, "Because of the simulated cache hit, must not go to the Db");
         Assert.AreEqual(currencycodes.Count, codes.Count(), "Must return the codes as-is");
      }
   }
}

The EFDbContext class has DbSet method

public class EFDbContext
{
public DbSet CurrencyCodes { get; set; }
}

This line:
mockEfContext.SetupGet(x => x.SomeCodes)
.Returns(currencycodes);
is throwing error.
Does the DbSet got to do anything?