assertTrue(result == 0 || TEN.pow(result - 1).compareTo(x) < 0);
      }
    }
  }

  // Relies on the correctness of log10(BigInteger, FLOOR).
  @GwtIncompatible // TODO
  public void testLog10Exact() {
    for (BigInteger x : POSITIVE_BIGINTEGER_CANDIDATES) {
      int logFloor = BigIntegerMath.log10(x, FLOOR);
      boolean expectSuccess = TEN.pow(logFloor).equals(x);
      try {