How to deal with private member accessor and collections?

Question

I have a class hierachy like this

public class A
{
    protected class B 
    {
        String Name { get; set; }
    }

    protected class C : KeyedCollection<String, B> 
    {
        // ...
    }

    protected C Collection { get; }

    // ...

    public A Copy () 
    {
        // Creates a deep copy of this instance.
    }
}

Now I'd like to write a unit test to compare if two instances of A have the same items B inside the property KeyedCollection. However, I'm not being able to perform a foreach loop into the A instances. What I had tried,

[TestClass]
public class TestClass
{
    public void ATest()
    {
        A original = new A();
        A copy = A.Copy();

        // ...

        A_Accessor originalAccessor = A_Accessor.AttachShadow(original);
        A_Accessor copyAccessor = A_Accessor.AttachShadow(copy);

        foreach(var originalItem in originalAccessor.Collection)
        {
            var copyItem = copyAccessor[originalItem.Name];
            Assert.AreEqual(originalItem, copyItem);
        }
    }
}

This code doesn't even compile because the C class accessor doesn't implements the IEnumerable interface (it doesn't implement any interface from KeyedCollection class). Does anyone have an idea about how can I overcome this issue?

The error message I'm getting is

foreach statement cannot operate on variables of type 'C' because 'A_Accessor.C' does not contain a public definition for 'GetEnumerator'

Answer 1

I just tried to compile your example: As expected I got an Error

Inconsistent accessibility: field type 'A.C' is less accessible than field 'A.Collection'.

Basically that means that you cannot declare a protected property using a private type. So it's not a problem with your test code but with the code to be tested ...

EDIT

You could use originalAccessor.Collection.Target and cast it to ICollection. Of course you can only enumerate over objects in this case, so you'll have to cast each item again:

foreach (var item in (originalAccessor.Collection.Target as ICollection)) {
   A_Accessor.B casted = A_Accessor.B.AttachShadow(item);
   var copyItem = copyAccessor[casted.Name];
   Assert.AreEqual(casted, copyItem);
}