I agree with Mike Weller. You should probably not be linking against the XCTest framework in your actual app code. Remove XCTest framework. Look at the linker errors and remove things that are referencing the framework. Wash, rinse, repeat.
If you have a test target, that is different. What can easily happen during the migration from SenTestKit to XCTest is having the wrong framework search path which causes linking against the Mac OS X framework instead of the iOS framework. This doesn’t work.
An easy way to see what the correct framework search path settings are is to create a dummy project, open the build settings for the Tests target and then filter for “Framework Search Path.”
I think the correct vanilla paths are:
$(SDKROOT)/Developer/Library/Frameworks (non-recursive)
$(inherited) (non-recursive)
$(DEVELOPER_FRAMEWORKS_DIR) (non-recursive)