Could not load type 'MapProvider' from assembly during .Net unit test

I'm receiving a System.开发者_JAVA技巧Configuration.ConfigurationErrorsException with the message Could not load type 'XxxSiteMapProvider' from assembly 'System.Web, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'.

I'm trying to unit test a separate class in the the same project as the XxxSiteMapProvider custom class. The error message indicates the proper point of the App.config for picking up the custom SiteMapProvider and I did a search across the solution and the class name is not duplicated anywhere. (I saw from searches that conflicting class names may cause this error.)

Any suggestions on how to debug this?

Try specifying the fully qualified type name for your SiteMap provider in the config in the following pattern.

<namespace>.<classname>, <fully qualified assembly name including public key>