Edit: just found out that -ObjC does the trick as well
Today I ran into this rather annoying issue when running some unit tests on Xcode:
+[Service dateHeaderContent]: unrecognized selector sent to class 0x1004b9280
After spending some time on what I was beginning to think was a wild goose chase, I found out about this little lovely
Place it on YourTestTarget > Build Settings > Linking > Other Linker Flags and it’ll fix the aforementioned issue.
If you want to know the "why", read it here.