如何编写单元测试

Question

我需要在此源代码上编写一些单元测试。

public class PagedCollection<T> : ReadOnlyCollection<T>, IPagedCollection<T>
{
    public int CurrentPage { get; }
    public int TotalPages { get; }
    public int PageSize { get; }
    public int TotalCount { get; }
    public bool HasPrevious => CurrentPage > 1;
    public bool HasNext => CurrentPage < TotalPages;

    public PagedCollection(ICollection<T> items, int count, int pageNumber, int pageSize) : base(items.ToList())
    {
        EnsureArg.IsGte(count, 0, nameof(count));
        EnsureArg.IsGt(pageNumber, 0, nameof(pageNumber));
        EnsureArg.IsGt(pageSize, 0, nameof(pageSize));

        TotalCount = count;
        CurrentPage = pageNumber;
        PageSize = pageSize;
        TotalPages = (int)Math.Ceiling(count / (double)pageSize);
    }
}

我还有1个关于单元测试的问题：模拟和存根有什么区别？