Unit testing Microsoft Moles：循环参考错误？

我有以下实体框架实体：

public class Country
{
    public long Id { get; set; }
    public string Code { get; set; }
    public virtual ICollection<Person> Persons { get; set; }
}

public class Person
{
    public long Id { get; set; }
    public long? Country_Id { get; set; }
    public Country HomeCountry { get; set; }
}

答案是：

MolesContext.ExecuteWithoutMoles(() => instance.Country_Id = id);

MolesContext.ExecuteWithoutMoles(() => instance.Country_Id = id);