C# Unit testing with Fake database context using a HashSet (pluralsight code)(New Q)

Question

The short version:

In this video, Mr. Scott Allen explains how to test a controller. But he does not show the full code of the class: FakeDbContext. Is there someone who can help me finish it? He shows the class at, 06:15 min in the video for "testing controllers".

The long version

At school I have a elective where we learn C#. My exam project is a ASP site using MVC3. To learn it fast, i have seen videos from PluralSight. My question is about some code that are in this video He explains how to test controllers. So i tried: I have made a controller which has a simple index method:

public class Round1Controller : Controller
{
    IDbContext _db;

    public Round1Controller()
    {
        _db = new Entities();
    }
    
    public Round1Controller(IDbContext db)
    {
        _db = db;
    }
    
    public ActionResult Index()
    {
        var model = _db.ELECTIVES.ToList();

        return View(model);
    }

As you can see i have already tried to make a context. The index method is the one i want to TEST. The next thing he does is to make a class called, FakeDbContext, in the test project.

But sadly he only show a part of the code, and i have used a lot of hours trying to figure out how he creates a get method to a HashSet.

Here is the code that you can see from the video:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using EESS.Models;

namespace EESS.Tests
{
class FakeDbContext : IDbContext
{
    public IQueryable<Restaurant> Restaurants
    {
        get { return _map.Get<Restaurant>().asQueryable(); }
        set { _map.Use<Restaurant>(value); }
    }
    public IQueryable<Review> Reviews
    {
        get { return _map.Get<Review>().asQueryable(); }
        set { _map.Use<Review>(value); }
    }

    public int SaveChanges()
    {
        ChangesSaved = true;
        return 0;
    }

    public bool ChangesSaved { get; set; }

    public T Attach<T>(T entity) where T : class
    {
        _map.Get<T>().Add(entity);
        return entity;
    }
    public T Add<T>(T entity) where T : class
    {
        _map.Get<T>().Add(entity);
        return entity;
    }

    public T Delete<T>(T entity) where T : class
    {
        _map.Get<T>().Remove(entity);
        return entity;
    }

    SetMap _map = new SetMap();

    class SetMap : KeyedCollection<Type, object>
    {
        public HashSet<T> Use<T>(IEnumerable<T> sourceData)
        {
            var set = new HashSet<T>(sourceData);
            if (Contains(typeof(T)))
            {
                Remove(typeof(T));
            }
            Add(set);
            return set;
        }
    }
}
}

To end the long version, my problem is i get a error on _Map.Get. Does not contain a definition or extension method.

EDIT! PART 2:

After @xelibrion great answer it finally worked.

But then another problem come up.

The IDbContext class looks like this:

public interface IDbContext
    {
        IQueryable<ELECTIVES> ELECTIVES { get; }
        int SaveChanges();
        T Attach<T>(T entity) where T : class;
        T Add<T>(T entity) where T : class;
        T Delete<T>(T entity) where T : class;
    }
    

When i add this interface to my Entities Class it offcouse expect me to implement the methods. PluralSight implements them like this:

public DbSet<ELECTIVES> electives { get; set; }

    IQueryable<ELECTIVES> IDbContext.ELECTIVES
    {
        get { return electives; }
    }

    int IDbContext.SaveChanges()
    {
        return SaveChanges();
    }
    
    T IDbContext.Add<T>(T entity)
    {
        return Set<T>().Add(entity);
    }
    
    T IDbContext.Delete<T>(T entity)
    {
        return Set<T>().Remove(entity);
    }
    
    T IDbContext.Attach<T>(T entity)
    {
        
        var entry = Entry(entity);
        entry.State = System.Data.EntityState.Modified;
        return entity;
        return Set<T>().Add(entity);
    }

But my "_dbModel.Designer.cs" class from my entity model does not know what Set and Entry is, and only suggest i make a method stub. There are a lot more code in this class, so if its need just ask for the rest :) I have changed Restaurants to Electives since thats the table name i my DB.

Is it a "using" i have forgotten? I have seen the video again, and he does not have a method stub in his DB class.

Answer 1

I suppose full version of SetMap class should look like this

class SetMap : KeyedCollection<Type, object>
{
    public HashSet<T> Use<T>(IEnumerable<T> sourceData)
    {
        var set = new HashSet<T>(sourceData);
        if (Contains(typeof(T)))
        {
            Remove(typeof(T));
        }
        Add(set);
        return set;
    }

    public HashSet<T> Get <T>()
    {
        return (HashSet<T>) this[typeof(T)];
    }

    protected override Type GetKeyForItem(object item)
    {
        return item.GetType().GetGenericArguments().Single();
    }
}