Reply to dyld: could not load inserted library libXCTestBundleInject.dylib I just hit this same situation. XCode 12.1 iPhoneOS 11 Pro Simulator iOS 14.1 I don't know which step fixed it but I... Deleted the app from the iPhone simulator Restarted the simulator with Device-> Restart from the menu Restarted tests Developer Tools & Services Xcode Oct ’21