@TestOnly
  void idInit(int length1, int length2) {
    myOriginalLengths[0] = length1;
    myOriginalLengths[1] = length2;
    myDiscardedLengths[0] = length1;
    myDiscardedLengths[1] = length2;
    for (int j = 0; j < 2; j++) {
      int originalLength = myOriginalLengths[j];
      myOldIndices[j] = new int[originalLength];
      for (int i = 0; i < originalLength; i++) {
        myOldIndices[j][i] = i;
      }
    }
  }
@TestOnly
  void idInit(int length1, int length2)