assertTrue(BigIntegerMath.isPowerOfTwo(result));
      assertTrue(result.compareTo(x) >= 0);
      assertTrue(result.compareTo(x.add(x)) < 0);
    }
  }

  public void testFloorPowerOfTwo() {
    for (BigInteger x : POSITIVE_BIGINTEGER_CANDIDATES) {
      BigInteger result = BigIntegerMath.floorPowerOfTwo(x);
      assertTrue(BigIntegerMath.isPowerOfTwo(result));
      assertTrue(result.compareTo(x) <= 0);

    int logFloor = x.bitLength() - 1;
    switch (mode) {
      case UNNECESSARY:
        checkRoundingUnnecessary(isPowerOfTwo(x)); // fall through
      case DOWN:
      case FLOOR:
        return logFloor;

      case UP:
      case CEILING:
        return isPowerOfTwo(x) ? logFloor : logFloor + 1;

      case HALF_DOWN:
      case HALF_UP:
      case HALF_EVEN:

   *
   * <p>This differs from {@code Integer.bitCount(x) == 1}, because {@code
   * Integer.bitCount(Integer.MIN_VALUE) == 1}, but {@link Integer#MIN_VALUE} is not a power of two.
   */
  public static boolean isPowerOfTwo(int x) {
    return x > 0 & (x & (x - 1)) == 0;
  }

  /**
   * Returns 1 if {@code x < y} as unsigned integers, and 0 otherwise. Assumes that x - y fits into

   * Long.bitCount(Long.MIN_VALUE) == 1}, but {@link Long#MIN_VALUE} is not a power of two.
   */
  @SuppressWarnings("ShortCircuitBoolean")
  public static boolean isPowerOfTwo(long x) {
    return x > 0 & (x & (x - 1)) == 0;
  }

  /**
   * Returns 1 if {@code x < y} as unsigned longs, and 0 otherwise. Assumes that x - y fits into a