Unit test fluent nhibernate ordered list mapping

Question

I get an exception when I try to unit test an ordered list with fluent nhibernate. The code seems to run ok but my PersistenceSpecification fails!

System.ApplicationException: Expected 'CareerNote.Core.Model.Section' but got 'CareerNote.Core.Model.Section' at position 0

The full code is on github: http://github.com/fodonnel/CareerNote/blob/master/src/CareerNote.Persistence.Tests/Mappings/SectionMapTests.cs

My class:

public partial class Section
{
    private Guid _id;
    private string _title = "";
    private Section _parent;
    private IList<Section> _children = new List<Section>();

    public virtual Guid Id
    {
        get { return _id; }
        set { _id = value; }
    }

    public virtual string Title
    {
        get { return _title; }
        set { _title = value + ""; }
    }

    public virtual Section Parent
    {
        get { return _parent; }
        set { _parent = value; }
    }

    public virtual IList<Section> Children
    {
        get { return _children; }
        set { _children = value; }
    }
}

Its Mapping:

public SectionMap()
{
    Id(x => x.Id).Column("SectionId")
       .GeneratedBy.Guid().UnsavedValue(Guid.Empty);

    Map(x => x.Title).Length(100).Access.CamelCaseField(Prefix.Underscore);

    References<Section>(x => x.Parent).Column("SectionParentId")
        .Access.CamelCaseField(Prefix.Underscore);

    HasMany<Section>(x => x.Children).KeyColumn("SectionParentId").Cascade.All()
        .Access.CamelCaseField(Prefix.Underscore)
        .AsList(index => index.Column("Position").Type<int?>());

}

The Test:

new PersistenceSpecification<Section>(new SessionProvider().GetSession())
    .CheckProperty(c => c.Title, "Title")
    .CheckList(c => c.Children, new List<Section> { new Section { Title = "C"} })
    .VerifyTheMappings();