Unfortunately the WP8 version of MonoGame doesn't support "Any CPU", so you have to switch back and forth between x86 (for running in the
emulator) and ARM (for running on a real device, and for publishing to the store).
Also found this link
http://forum.unity3d.com/threads/solved-store-test-kit-error.261000/[
^]
Unfortunate, but it looks like I just need to skip over the automated tests. This seems a little strange since this stuff worked just fine under VS Express for WP7.