def findAllHelper[T](tester: Tester[T], set: Set[T]): Set[T] = {
    if (tester.contains(set)) {
        if (set.size == 1) {
            return set
        } else {
          val splitSet = set.splitAt(set.size / 2)
          return findAllHelper(tester, splitSet._1) ++ findAllHelper(tester, splitSet._2)
        }
    } else {
      return Set()
    }

    }

  def findAll[T](tester: Tester[T]): Set[T] = findAllHelper(tester, tester.domain)