private List<Address> createValidatorList(
      final Address localAddr, final int countLower, final int countHigher) {
    final List<Address> result = new ArrayList<>();

    // Note: Order of this list is irrelevant, is sorted by value later.
    result.add(localAddr);

    for (int i = 0; i < countLower; i++) {
      result.add(AddressHelpers.calculateAddressWithRespectTo(localAddr, i - countLower));
    }

    for (int i = 0; i < countHigher; i++) {
      result.add(AddressHelpers.calculateAddressWithRespectTo(localAddr, i + 1));
    }

    result.sort(null);
    return result;
  }
This creates a list of validators, with the a number of validators above and below the local
address. The returned list is sorted.

@param localAddr The address of the node which signed the parent block
@param countLower The number of validators which have a higher address than localAddr
@param countHigher The number of validators which have a lower address than localAddr
@return A sorted list of validators which matches parameters (including the localAddr).
consensus/common/src/test/java/org/hyperledger/besu/consensus/common/bft/blockcreation/ProposerSelectorTest.java