My unit tests run fine when the target is set to 6.1, and the code itself is fine when I walk through the features in the simulator.
I think the problem is that the unit tests are expecting the 6.1 SDK to be there, but it's actually using the 5.1 SDK.
Here's the error:
dyld: Symbol not found: _objc_setProperty_nonatomic_copy
Referenced from: /Users/{my username}/Library/Developer/Xcode/DerivedData/{my app name}/Build/Products/Debug-Live-iphonesimulator/AgrianUnitTest.octest/AgrianUnitTest
Expected in: /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator5.1.sdk/System/Library/Frameworks/Foundation.framework/Foundation
My first thought was to change the Base SDK in my Unit Tests target, but I don't have any options other than Latest and 6.1 (manually entering 5.1 results in "SDK not found").