您是否将存储库模式与Entity Framework一起使用？

Question

Some people say we shouldn't use repository and unit of work patter because repository & UnitOfWork just duplicates what Entity Framework (EF) DbContext give you anyway. But if I use repositories I can write easy unit test for services because I can mock methods from repositories (which return data from database using linq queries), for example:

Repository:

public class CommentsRepository : ICommentsRepository
{
    public CommentsRepository(DatabaseContext context)
        : base(context)
    {
    }

    public IEnumerable<Comment> GetComments()
    {
        return context.Comments.Include(x => x.Note).OrderByDescending(x => x.CreatedDate).ToList();
    }
}

Service:

public class CommentsService : ICommentsService
{
    private ICommentsRepository _commentsRepository;

    public CommentsService(ICommentsRepository commentsRepository)
    {
        _commentsRepository = commentsRepository;
    }

    public IEnumerable<Comment> GetComments()
    {
        List<Comment> comments = _commentsRepository.GetComments().ToList();

        comments.ForEach(x => x.Author = "Secret");

        return comments;
    }
}

Unit test for service:

[TestClass]
public class CommentsServiceTest
{
    [TestMethod]
    public void GetCommentsTest()
    {
        // Arrange
        IList<Comment> comments = Builder<Comment>.CreateListOfSize(2)
            .Build();

        AutoMoqer mocker = new AutoMoqer();
        mocker.GetMock<ICommentsRepository>()
                .Setup(x => x.GetComments())
                .Returns(comments);

        // Act
        ICommentsService commentsService = mocker.Resolve<CommentsService>();
        IList<Comment> result = commentsService.GetComments().ToList();

        // Assert
        Assert.AreEqual("Secret", result[0].Author);
        Assert.AreEqual("Secret", result[1].Author);
    }
}

Now when I eliminate repository I must write linq queries inside services:

public class CommentsService : ICommentsService
{
    private DatabaseContext _context;

    public CommentsService(DatabaseContext context)
    {
        _context = context;
    }

    public IEnumerable<Comment> GetComments()
    {
        List<Comment> comments = _context.Comments.Include(x => x.Note).OrderByDescending(x => x.CreatedDate).ToList();

        comments.ForEach(x => x.Author = "Secret");

        return comments;
    }
}

Writing unit test for that service is problematic because I must mock:

context.Comments.Include(x => x.Note).OrderByDescending(x => x.CreatedDate)

So what do you do? Do you write repository classes or not? If not, how do you mock linq queries?

Answer 1

As with all patterns, if it suits your purposes then you should use it.

I wrote a unit of work and repository pattern implementation that wrapped Entity Framework. Not only so I could do tests, but to abstract EF away from the rest of my application.

It made later switching to an in memory database for 'live' testing an absolute breeze.