The model item passed into the dictionary is of type 'System.Collections.Generic.List' but this dictionary requires a model item of type 'System.Collections.Generic.IEnumberable'

I have an MVC 4 application that has a model developed using EF 5.0 (Code First).  I am investigating TDD and had to make changes to the code generated by the model in order to get my unit tests to work.  Now that my unit tests work I am getting the following error when I try and run the application.

System.InvalidOperationException: The model item passed into the dictionary is of type 'System.Collections.Generic.List`1[AppCatalog.Models.AppCatalog_Database]', but this dictionary requires a model item of type 'System.Collections.Generic.IEnumerable`1[AppCatalogData.AppCatalog_Database]'.

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Here is my controller:

namespace AppCatalog.Controllers
{
    public class DBCatalogController : Controller
    {
        private IAppCatalog db { get; set; }

        public DBCatalogController(IAppCatalog dataContext = null)
        {
            db = dataContext ?? new AppCatalogContainer();
        }
        public DBCatalogController()
        {
            db = new AppCatalogContainer();
        }

        //
        // GET: /DBCatalog/

        public ViewResult Index()
        {
            ViewBag.Title = "Application Catalog -> Database Catalog";

            var appcatalog_database = db.AppCatalog_Database.Include(a => a.AppCatalog_ServerType);
            return View(appcatalog_database.ToList());
        }
   }
}

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Here is the model definition in my view:

@model IEnumerable<AppCatalogData.AppCatalog_Database>

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Here is my Interface definition:

namespace AppCatalog.Models 
{
    public interface IAppCatalog 
    {
        IDbSet<AppCatalog_Database> AppCatalog_Database { get; set; }
        IDbSet<AppCatalog_ServerType> AppCatalog_ServerType { get; set; }
        IDbSet<AppCatalog_DBConnection> AppCatalog_DBConnection { get; set; }
        IDbSet<AppCatalog_Environment> AppCatalog_Environment { get; set; }
        IDbSet<AppCatalog_PIIData> AppCatalog_PIIData { get; set; }
        IDbSet<AppCatalog_Application> AppCatalog_Application { get; set; }
        IDbSet<AppCatalog_ApplicationTable> AppCatalog_ApplicationTable { get; set; }

        int SaveChanges();
        void Dispose();
    }

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Here is the AppCatalogContainer definition:

namespace AppCatalog.Models
{
    using System;
    using System.Data.Entity;
    using System.Data.Entity.Infrastructure;
    
    public partial class AppCatalogContainer : DbContext, IAppCatalog
    {
        public AppCatalogContainer()
            : base("name=AppCatalogContainer")
        {
        }
    
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            throw new UnintentionalCodeFirstException();
        }
    
        public IDbSet<AppCatalog_Database> AppCatalog_Database { get; set; }
        public IDbSet<AppCatalog_ServerType> AppCatalog_ServerType { get; set; }
        public IDbSet<AppCatalog_DBConnection> AppCatalog_DBConnection { get; set; }
        public IDbSet<AppCatalog_Environment> AppCatalog_Environment { get; set; }
        public IDbSet<AppCatalog_PIIData> AppCatalog_PIIData { get; set; }
        public IDbSet<AppCatalog_Application> AppCatalog_Application { get; set; }
        public IDbSet<AppCatalog_ApplicationTable> AppCatalog_ApplicationTable { get; set; }
    }
}

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I'm not sure what change I need to make to the View or the Controller to get this to work.  Everything worked fine until I made the changes for the unit testing.

Any help is greatly appreciated!