Why DbContext doesn't implement IDbContext interface?

Question

Why there is no IDbContext interface in the Entity Framework? Wouldn't it be easier to test things if there was an existing interface with methods like SaveChanges() etc. from which you could derive your custom database context interface?

public interface ICustomDbContext : IDbContext
{
    // add entity set properties to existing set of methods in IDbContext
    IDbSet<SomeEntity> SomeEntities { get; }
}

Answer 1

I see this IDbContext:

See this link And then you make a new partial class for your Entities Context With That interface.

public partial class YourModelEntities : DbContext, IDbContext 

EDITED: I edited this post, This Works for me. My Context

namespace dao
{
    public interface ContextI : IDisposable
    {
        DbSet<TEntity> Set<TEntity>() where TEntity : class;
        DbSet Set(Type entityType);
        int SaveChanges();
        IEnumerable<DbEntityValidationResult> GetValidationErrors();
        DbEntityEntry<TEntity> Entry<TEntity>(TEntity entity) where TEntity:class;
        DbEntityEntry Entry(object entity);
        string ConnectionString { get; set; }
        bool AutoDetectChangedEnabled { get; set; }
        void ExecuteSqlCommand(string p, params object[] o);
        void ExecuteSqlCommand(string p);
    }
}

YourModelEntities is your auto-generated partial class, and your need to create a new partial class with the same name, then add your new context interface, for this example is ContextI

NOTE: The interface hasn't implement all methods, because the methods are implemented in your auto-generate code.

namespace dao
{
    public partial class YourModelEntities :DbContext, ContextI
    {
        public string ConnectionString
        {
            get
            {
                return this.Database.Connection.ConnectionString;
            }
            set
            {
                this.Database.Connection.ConnectionString = value;
            }
        }

        bool AutoDetectChangedEnabled
        {
            get
            {
                return true;
            }
            set
            {
                throw new NotImplementedException();
            }
        }

        public void ExecuteSqlCommand(string p,params object[] os)
        {
            this.Database.ExecuteSqlCommand(p, os);
        }

        public void ExecuteSqlCommand(string p)
        {
            this.Database.ExecuteSqlCommand(p);
        }

        bool ContextI.AutoDetectChangedEnabled
        {
            get
            {
                return this.Configuration.AutoDetectChangesEnabled;
            }
            set
            {
                this.Configuration.AutoDetectChangesEnabled = value;
            }
        }

    }
}