如何将测试集成到使用ASP.NET Provider Model编写的代码中？

I'm fairly new to unit testing. I have a site built in the 3-tier architecture, UI -> BLL -> DAL. And I used the asp.net Provider Model, so by making changes to web.config I can switch to DAL dll to target different data sources, to be complete the DAL is written with Entity Framework.I'm fairly new to unit testing. I have a site b