Mocking Database transactions?

I have spent few hours trying to figure it out, I believed it can be done by MS Fakes directly without wrapper or new classe.

You need to do three steps:

1. Create shim object for DbContextTransaction, and detour its Commit and Rollback methods to do nothing.
2. Create shim object for Database. And detour its BeginTransaction method to return DbContextTransaction shim object created in step 1.
3. Detour DbContext.Database property for all instances to return Database shim object created in step 2.

And that all.

    static void SetupDBTransaction()
    {
        System.Data.Entity.Fakes.ShimDbContextTransaction transaction = new System.Data.Entity.Fakes.ShimDbContextTransaction();
        transaction.Commit = () => { };
        transaction.Rollback = () => { };

        System.Data.Entity.Fakes.ShimDatabase database = new System.Data.Entity.Fakes.ShimDatabase();
        database.BeginTransactionIsolationLevel = (isolationLevel) =>{return transaction.Instance;};

        System.Data.Entity.Fakes.ShimDbContext.AllInstances.DatabaseGet = (@this) => { return database.Instance; };
    }

Testing this kind of stuff is always complicated, but first of all you should ask yourself if you want to unit test your business logic or if you want to integration test your application.

If you want to unit test your logic, you basically shouldn't even try to mock entity framework, because you do not want to test EF, you just want to test your code, right? To do so, mock any data access object and only unit test your business logic.

But if you want to test if your data access layer works, e.g. if your code can handle all the CRUD operations you have implemented, you should do integration tests against a real database. Do not try to mock any data access objects (EF) in this case, simply run you tests against a test database or a sql-express localDB for example.

You can wrap the context and the transaction in an Interface and then implement the interface by some provider class:

public interface IDbContextProvider
{
    YourContext Context { get; set; }
    DbContextTransaction DbTransaction { get; set; }
    void Commit();
    void Rollback();
    void BeginTransaction();
    void SaveChanges();
}

and then implement it:

public class EfContextProvider : IDbContextProvider
{
    public EfContextProvider(YourContext context)
    {
        Context = context;
    }
    public YourContext Context { set; get; }
    public DbContextTransaction DbTransaction { set; get; }

    public void Commit()
    {
        DbTransaction.Commit();
    }

    public void Rollback()
    {
        DbTransaction.Rollback();
    }

    public void BeginTransaction()
    {
        DbTransaction=Context.Database.BeginTransaction();
    }

    public void SaveChanges()
    {
        Context.SaveChanges();
    }
}

so now give your class the IDbContextProvider dependency and work with it (It has also the context inside) . Maybe substitute the using block with _contextProvider.BeginTransaction(); and then also _contextProvider.Commit(); or _contextProvider.Rollback();