Moq无法解析ICollection参考

Question

I am using Moq.4.2.1507.0118 and I'm having a problem that I have not seen before. The situation is that I have two classes in my model (A and B) with a one to many relationship. For example:

[Table("A")]
public partial class A
{

    public A()
    {
        this.theB = new HashSet<B>();
    }

    [Key]
    public int AId{ get; set; }
    public string Name{ get; set; }

    public virtual ICollection<B> theB{ get; set; }

}

[Table("B")]
public partial class B
{
    [Key]
    public int BId{ get; set; }
    public int AId{ get; set; }
    public virtual A theA { get; set; }
}

Of course I also have the DbSet's defined in the DbContext.

Then, in my test code, I have:

    [TestMethod]
    public void SomeTest()
    {
        var theAs = new List<A>
        {
            new A{ AId=1, Name="test" }
        };
        var theBs= new List<B>
        {
            new B{ BId=1, AId=1, theA=theAs[0] }
        };

        var ASet= new Mock<DbSet<A>>().SetupData(theAs);
        var BSet= new Mock<DbSet<B>>().SetupData(theBs);

        var context = new Mock<MyContext>();
        context.Setup(s => s.A).Returns(ASet.Object);
        context.Setup(s => s.B).Returns(BSet.Object);

        var m = new ClassThatImTesting(context);
        m.someMethod("test");
    }

Normally I would see that this is enough to let A and B know about each other in the mock context. However, in the method that I'm testing, if I run something like this:

var result = context.A.Where(x => x.theB.Count() > 0).FirstOrDefault();

I get null. Since I've done this in so many other tests without a problem, I'm having a hard time seeing what I've done to trip this up. Any ideas would be helpful! I've simplified this example from my actual code, so please forgive syntax errors.

Answer 1

You need to instantiate the collection to the A object before injecting the context to the class.

    [TestMethod]
    public void SomeTest()
    {
        var theAs = new List<A>
        {
            new A{ AId=1, Name="test" }
        };
        var theBs= new List<B>
        {
            new B{ BId=1, AId=1, theA=theAs[0] }
        };
        //here
        theAs[0].theB = theBs

        var ASet= new Mock<DbSet<A>>().SetupData(theAs);
        var BSet= new Mock<DbSet<B>>().SetupData(theBs);

        var context = new Mock<MyContext>();
        context.Setup(s => s.A).Returns(ASet.Object);
        context.Setup(s => s.B).Returns(BSet.Object);

        var m = new ClassThatImTesting(context);
        m.someMethod("test");
    }