The unit test failed, as expected. Then I put the actual code into the extension method, and ran the test again. The test still failed. I looked through the code and everything seemed right to me, so I put a breakpoint into the unit test and tried to debug it. But my breakpoint did not get hit; I get the message, "No symbols have been loaded for this document."
I've tried deleting the DLLs manually, rebuilding the solution, restarting VS 2008, rebooting, and every combination I can think of. I cannot find a way to get it to load symbols for my unit test and hit my breakpoint.