Hi, I know it's an old question, but in case somebody faces the same problem. You can use method swizzling to address this issue. private let swizzling: (CKRecord.Type) -> Void = { record in   guard let originalMethod = class_getInstanceMethod(record, #selector(getter: CKRecord.recordChangeTag)),      let swizzledMethod = class_getInstanceMethod(record, #selector(CKRecord.swizzledRecordChangeTag))      else { return }       method_exchangeImplementations(originalMethod, swizzledMethod) } extension CKRecord {   class func doBadSwizzleStuff() {     swizzling(self)   }       @objc func swizzledRecordChangeTag() -> String? {     "123"   } } And then call at your test setup: CKRecord.doBadSwizzleStuff()