Hi All,
I've faced the same problem again and again, I assume is a kind of bug of STS, It happens to me when I try to launch unit test from IDE, and when the problem arises what I do is a "maven clean install" from outside of the IDE, refresh the project folder (F5) in Eclipse, and relaunch the unit tests... and it works!
So don't get crazy searching a miss-configuration in your application context xml file, I'm pretty sure this bug has to do with eclipse maven plugin + spring plugin... who knows..