EF6 DbSet< T>在Moq中返回null [英] EF6 DbSet<T> returns null in Moq

问题描述

我的应用程序中使用DbContext(EF6)进行了典型的存储库模式设置:

I have a typical Repository Pattern setup in my application with a DbContext (EF6):

public class MyDbContext : EFContext<MyDbContext> {

    public MyDbContext () { }

    public virtual DbSet<CartItem> Cart { get; set; }

和一个存储库:

public class GenericEFRepository<TEntity, TContext>
    where TEntity : class, new()
    where TContext : EFContext<TContext> {

    private readonly TContext _context;

    public GenericEFRepository(TContext context) {
        _context = context;
    }
    //...
    public virtual TEntity Insert(TEntity item) {
        return _context.Set<TEntity>().Add(item);
    }

我正在用Moq 4.2(通过本教程)对此进行测试，方法是创建一个模拟上下文:

I'm testing this with Moq 4.2 (following this tutorial) by creating a mock context:

        // Arrange
        var mockSet = new Mock<DbSet<CartItem>>();

        var mockContext = new Mock<MyDbContext>();
        mockContext.Setup(c => c.Cart).Returns(mockSet.Object);

        // Act
        var service = new GenericEFRepository<CartItem, MyDbContext>(mockContext.Object);
        service.Insert(new CartItem() {
            Id = 1,
            Date = DateTime.Now,
            UserId = 1,
            Detail = string.Empty
        });

        // Assert
        mockSet.Verify(s => s.Add(It.IsAny<CartItem>()), Times.Once());

问题是，当我到达此行时:

The problem is that when I reach this line:

return _context.Set<TEntity>().Add(item);

_context.Set<TEntity>()返回null.经过一番谷歌搜索之后，似乎在EF5中有必要返回IDbSet<T>以便Moq模拟该集合，但不是使用EF6.是不是这样，还是我想念一些东西?

_context.Set<TEntity>() returns null. After some googling it seems in EF5 it was necessary to return IDbSet<T> for Moq to mock the set, but not with EF6. Is this not the case, or am I missing something?

推荐答案

为Set<T>()方法添加设置:

mockContext.Setup(c => c.Set<CartItem>()).Returns(mockSet.Object);

即使在真实的EFContext上，属性Cart和Set<CartItem>()指向同一对象，上下文的 mock 也不知道，所以您需要告诉它明确返回什么.

Even though on the real EFContext the property Cart and Set<CartItem>() refer to the same object, the mock of the context doesn't know that, so you need to tell it explicitly what to return.

由于它是一个宽松的模拟，因此对尚未设置的方法的调用将返回默认值，在这种情况下为null.严格的模拟可以很好地帮助发现此错误，但是具有其他人不愿处理的维护成本.

Since it was a loose mock, the call to a method that hasn't been setup returns the default value, which in this case is null. Strict mocks are nice in helping find this error, but also have maintenance costs that other folks don't want to deal with.

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