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Fake DbContext of Entity Framework 4.1 to Test

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再見小時候
再見小時候 2020-11-22 17:19

I\'m using this tutorial to Fake my DbContext and test: http://refactorthis.wordpress.com/2011/05/31/mock-faking-dbcontext-in-entity-framework-4-1-with-a-generic-repository/

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  • 攒了一身酷
    攒了一身酷 (楼主)
    2020-11-22 17:44

    I know we shouldn't do it but sometimes you have to anyway (your boss might ask you too for instance and wouldn't change his mind).

    So as I had to do it I leave it here it might help some people. I'm quite new to c# / .net and all so it's far from being optimized/clean I suppose but it seems to work.

    following MSDN Find here the missing class and using a bit of reflection I managed to add one way properties : Key elements here are the AddNavigationProperty and RefreshNavigationProperties. If anyone has suggestion to improve this code I'll gladly take them 

    using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Data.Entity;
using System.Data.Entity.Infrastructure;
using System.Linq;
using System.Linq.Expressions;

namespace MockFactory
{
    public class TestDbSet : DbSet, IQueryable, IEnumerable, IDbAsyncEnumerable
        where TEntity : class
    {
        public readonly ObservableCollection _data;
        private readonly IQueryable _query;
        private readonly Dictionary entities;

        public TestDbSet()
        {
            _data = new ObservableCollection();
            _query = _data.AsQueryable();

            entities = new Dictionary();
        }

        public override ObservableCollection Local
        {
            get { return _data; }
        }

        IDbAsyncEnumerator IDbAsyncEnumerable.GetAsyncEnumerator()
        {
            return new TestDbAsyncEnumerator(_data.GetEnumerator());
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return _data.GetEnumerator();
        }

        Type IQueryable.ElementType
        {
            get { return _query.ElementType; }
        }

        Expression IQueryable.Expression
        {
            get { return _query.Expression; }
        }

        IQueryProvider IQueryable.Provider
        {
            get { return new TestDbAsyncQueryProvider(_query.Provider); }
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return _data.GetEnumerator();
        }

        public void AddNavigationProperty(DbSet dbSet) where T : class
        {
            entities.Add(typeof (T), dbSet);
        }

        public void RefreshNavigationProperty(TEntity item)
        {
            foreach (var entity in entities)
            {
                var property = item.GetType().GetProperty(entity.Key.Name);

                var type =
                    (int)item.GetType().GetProperty(entity.Key.Name.Replace(typeof(TEntity).Name, "")).GetValue(item);

                var dbSets = (IEnumerable)entity.Value.GetType().GetField("_data").GetValue(entity.Value);

                var dbSet = dbSets.Single(x => (int)x.GetType().GetProperty("Id").GetValue(x) == type);
                property.SetValue(item, dbSet);
            }
        }

        public override TEntity Add(TEntity item)
        {
            RefreshNavigationProperty(item);
            _data.Add(item);
            return item;
        }

        public override TEntity Remove(TEntity item)
        {
            _data.Remove(item);
            return item;
        }

        public override TEntity Attach(TEntity item)
        {
            _data.Add(item);
            return item;
        }

        public override TEntity Create()
        {
            return Activator.CreateInstance();
        }

        public override TDerivedEntity Create()
        {
            return Activator.CreateInstance();
        }
    }
}



    You can then create your context
    


     public TestContext()
        {
            TypeUsers = new TestDbSet();
            StatusUsers = new TestDbSet();

            TypeUsers.Add(new TypeUser {Description = "FI", Id = 1});
            TypeUsers.Add(new TypeUser {Description = "HR", Id = 2});

            StatusUsers.Add(new StatusUser { Description = "Created", Id = 1 });
            StatusUsers.Add(new StatusUser { Description = "Deleted", Id = 2 });
            StatusUsers.Add(new StatusUser { Description = "PendingHR", Id = 3 });


            Users = new TestDbSet();

            ((TestDbSet) Users).AddNavigationProperty(StatusUsers);
           ((TestDbSet)Users).AddNavigationProperty(TypeUsers);

        }

        public override DbSet TypeUsers { get; set; }
        public override DbSet StatusUsers { get; set; }
        public override DbSet Users { get; set; }
        public int SaveChangesCount { get; private set; }

        public override int SaveChanges(string modifierId)
        {
            SaveChangesCount++;
            return 1;
        }
    }

    


    Finally do not forget in your test to refresh the navigation properties before doing the assert (there should be a better way but I couldn't find it )
    


    ContextFactory.Entity.Users.Each(((TestDbSet) ContextFactory.Entity.Users).RefreshNavigationProperty);

    
    
    
             
    
                                                        
    
            
            
    
              
                
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