C# 解耦EntityFramework进行单元测试

1. 首先ef的repository需要抽象的行为提到接口中。

例如 ：

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; }
	...
}

然后就可以使用DataContext和TestDataContext实现这个接口。其中TestDataContext是在UT中使用的，DataContext是自动生成的。

TestDataContext还需要以下几个类进行模拟。
 

 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; }
        }
    }

使用示例：

[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);
        }

如果使用了存储过程，需要额外定义存储过程的接口。
例如：

IStorePro {
...
}

StorePro : IStorePro{
...
}

StoreProFake: IStorePro{

}

然后IDataContext负责返回存储过程的实例

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

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