C# decouples EntityFramework for unit testing

1. First of all, EF's Repository needs abstract behavior to be mentioned in the interface.

For example:

public interface IXXXContext : IDisposable
    {
        IXXXContext NewInstance();
// db sets
        DbSet<AAABBB> aaa { get; set; }
...
// common 
Database Database { get; }
        DbContextConfiguration Configuration { get; }
        int SaveChanges();


        Task<int> SaveChangesAsync();


	// store pros
...
        IStorePro1 StorePro1 { get; }
	...
}

Then you can use DataContext and TestDataContext to implement this interface. Among them, TestDataContext is used in UT, and DataContext is automatically generated.

TestDataContext also requires the following classes for simulation.

 public class TestDbSet<TEntity> : DbSet<TEntity>, IQueryable, IEnumerable<TEntity>, IDbAsyncEnumerable<TEntity>
         where TEntity : class
    {
        ObservableCollection<TEntity> _data;
        IQueryable _query;


        public TestDbSet()
        {
            _data = new ObservableCollection<TEntity>();
            _query = _data.AsQueryable();
        }


        public override TEntity Add(TEntity 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<TEntity>();
        }


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


        public override ObservableCollection<TEntity> Local
        {
            get { return _data; }
        }


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


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


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


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


        IEnumerator<TEntity> IEnumerable<TEntity>.GetEnumerator()
        {
            return _data.GetEnumerator();
        }


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


    internal class TestDbAsyncQueryProvider<TEntity> : IDbAsyncQueryProvider
    {
        private readonly IQueryProvider _inner;


        internal TestDbAsyncQueryProvider(IQueryProvider inner)
        {
            _inner = inner;
        }


        public IQueryable CreateQuery(Expression expression)
        {
            return new TestDbAsyncEnumerable<TEntity>(expression);
        }


        public IQueryable<TElement> CreateQuery<TElement>(Expression expression)
        {
            return new TestDbAsyncEnumerable<TElement>(expression);
        }


        public object Execute(Expression expression)
        {
            return _inner.Execute(expression);
        }


        public TResult Execute<TResult>(Expression expression)
        {
            return _inner.Execute<TResult>(expression);
        }


        public Task<object> ExecuteAsync(Expression expression, CancellationToken cancellationToken)
        {
            return Task.FromResult(Execute(expression));
        }


        public Task<TResult> ExecuteAsync<TResult>(Expression expression, CancellationToken cancellationToken)
        {
            return Task.FromResult(Execute<TResult>(expression));
        }
    }


    internal class TestDbAsyncEnumerable<T> : EnumerableQuery<T>, IDbAsyncEnumerable<T>, IQueryable<T>
    {
        public TestDbAsyncEnumerable(IEnumerable<T> enumerable)
            : base(enumerable)
        { }


        public TestDbAsyncEnumerable(Expression expression)
            : base(expression)
        { }


        public IDbAsyncEnumerator<T> GetAsyncEnumerator()
        {
            return new TestDbAsyncEnumerator<T>(this.AsEnumerable().GetEnumerator());
        }


        IDbAsyncEnumerator IDbAsyncEnumerable.GetAsyncEnumerator()
        {
            return GetAsyncEnumerator();
        }


        IQueryProvider IQueryable.Provider
        {
            get { return new TestDbAsyncQueryProvider<T>(this); }
        }
    }


    internal class TestDbAsyncEnumerator<T> : IDbAsyncEnumerator<T>
    {
        private readonly IEnumerator<T> _inner;


        public TestDbAsyncEnumerator(IEnumerator<T> inner)
        {
            _inner = inner;
        }


        public void Dispose()
        {
            _inner.Dispose();
        }


        public Task<bool> MoveNextAsync(CancellationToken cancellationToken)
        {
            return Task.FromResult(_inner.MoveNext());
        }


        public T Current
        {
            get { return _inner.Current; }
        }


        object IDbAsyncEnumerator.Current
        {
            get { return Current; }
        }
    }

Usage example:

[TestMethod]
        public void TestMethod1()
        {
            var mockSet = new Mock<DbSet<BLACKLISTED_TICKET>>();
            var mockContext = new Mock<TicketDataContextTest>();
            mockContext.Setup(m => m.BLACKLISTED_TICKET).Returns(new TestDbSet<BLACKLISTED_TICKET>());


            var context = mockContext.Object;


            context.BLACKLISTED_TICKET.Add(new BLACKLISTED_TICKET()
            {
                TicketNumber = "aaa",
                CreatedDateTime = DateTime.Now,
                Id = 1,
                ModifiedDateTime = DateTime.Now,
                STATUS = "1"
            });


            Assert.IsTrue(context.BLACKLISTED_TICKET.First().Id == 1);
        }

If a stored procedure is used, an additional interface for the stored procedure needs to be defined.
For example:

IStorePro {
...
}


StorePro : IStorePro{
...
}


StoreProFake: IStorePro{


}

Then IDataContext is responsible for returning the instance of the stored procedure

IDataContext{
	...
	IStorePro GetStorePro();
	...
}

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