I created a new Cocoa Touch Static Library project with Unit Testing in XCode 4 and added a category:
// NSString+Inflections.h @interface NSString (Inflect
I had the same situation when i was working in the Objective-c project. I did the following steps and it went well.
1) Select the project and goto target.
2) select Test target and add -ObjC like showing in the image.
-ObjC
3) Now try to run the unit XCTest.