@Override
  @SuppressWarnings("unused")
  public Comparator<BlockHeader> getBlockChoiceRule() {
    return (a, b) -> {
      throw new NonDeterministicOperationException(
          "ReferenceTestBlockchain for VMTest Chains do not support fork choice rules");
    };
  }
An exception thrown for methods not supported by the T8nBlockchain.
ethereum/evmtool/src/main/java/org/hyperledger/besu/evmtool/t8n/T8nBlockchain.java