}

  public void testToString() {
    String[] tests = {
      "0",
      "ffffffffffffffff",
      "7fffffffffffffff",
      "ff1a618b7f65ea12",
      "5a4316b8c153ac4d",
      "6cf78a4b139a4e2a"
    };
    int[] bases = {2, 5, 7, 8, 10, 16};
    for (int base : bases) {
      for (String x : tests) {
        BigInteger xValue = new BigInteger(x, 16);
        long xLong = xValue.longValue(); // signed