Question

I want to write unit test for a class that contains linq to sql codes . I mean inside each method I have created a new DbContext and done database jobs .

I searched the web . first I came to use repository and Unit of Work patterns but I figured out that DbContext itself is a unit of work and its dbset works as repositories . another point is that I think there is no need to test Linq part because it works as it should ( tested by .net team ) . I want to test the logic I have added to the code . so I decided to create an interface with necessary methods with two implementations , one uses linqToSql while another is just a mock . something like this :

    public interface IDbManager
    {
        bool Insert(MyEntity newEntity);
    }

    public class RealDbManager:IDbManager
    {
        public bool Insert(MyEntity newEntity)
        {
            using (DbDataContext db = new DbDataContext())
            {
                db.MyEntities.InsertOnSubmit(newEntity);
                db.SubmitChanges();
            }
        }
    }

    public class MockDbManager:IDbManager
    {
        public bool Insert(MyEntity newEntity)
        {
            return true;
        }
    }

is the whole idea correct ? if so is this a correct implementation ?

is it possible to define DbDataContext as a class variable instead of creating new instance inside each method ?

Answer 1

You have the right general idea for a start. Your Mock Insert method should save the entity to some in-memory store so that subsequent queries will return the inserted information, as would be expected. But the very basic idea of having an interface, with a ‘real’ and a ‘mock’ implementation is there.

Remember that when using your Mock in tests, you are testing your other code that uses the mock – not the mock itself.

As for defining the DataContext as a member variable; you could use an IDisposable pattern for it, like so:

public class RealDbManager:IDbManager, IDisposable
{
    DbDataContext db = new DbDataContext();
    public bool Insert(MyEntity newEntity)
    {
        {
            db.MyEntities.InsertOnSubmit(newEntity);
            db.SubmitChanges();
        }
    }
    public void Dispose()
    {
        db.Dispose();
    }
}

You would just have to be sure to dispose of your DbManager, then.