### Question:
ByteUtils { public static byte[] bigIntToByteArrayLeadingZeros(final BigInteger value, final int numBytes) { return byteArrayLeadingZeros(value.toByteArray(), numBytes); } private  ByteUtils(); static byte[] bigIntToByteArrayLeadingZeros(final BigInteger value, final int numBytes); static byte[] byteArrayLeadingZeros(byte[] valueByteArray, int numBytes); static byte[] bigIntToBytes(final BigInteger x); static byte[] longToBytes(final long x); static int bytesToInt(final byte[] bytes); static byte[] intToBytes(final int x); static byte[] shortToBytes(final short x); static int isEqualConstantTime(final int b, final int c); static int isNegativeConstantTime(final int b); static String toString(final byte[] bytes);  }### Answer:
@Test public void bigIntToByteArrayLeadingZeros() { assertBigIntToByteArrayLeadingZeros("00137c7c32", 6, "0000137C7C32"); assertBigIntToByteArrayLeadingZeros("00137c7c32", 5, "00137C7C32"); assertBigIntToByteArrayLeadingZeros("00137c7c32", 4, "137C7C32"); assertBigIntToByteArrayLeadingZeros("00137c7c32", 3, null); assertBigIntToByteArrayLeadingZeros("0137c7c32", 6, "0000137C7C32"); assertBigIntToByteArrayLeadingZeros("0137c7c32", 5, "00137C7C32"); assertBigIntToByteArrayLeadingZeros("0137c7c32", 4, "137C7C32"); assertBigIntToByteArrayLeadingZeros("0137c7c32", 3, null); assertBigIntToByteArrayLeadingZeros("137c7c32", 6, "0000137C7C32"); assertBigIntToByteArrayLeadingZeros("137c7c32", 5, "00137C7C32"); assertBigIntToByteArrayLeadingZeros("137c7c32", 4, "137C7C32"); assertBigIntToByteArrayLeadingZeros("137c7c32", 3, null); }