### Question:
RLP { public static byte[] encodeLong(long l) { if ((l & 0x00000000FFFFFFFFL) == l) { return encodeInt((int) l); } else { byte[] out = new byte[9]; out[0] = (byte) (OFFSET_SHORT_ITEM + 8); for (int i = 8; i > 0; i--) { out[i] = (byte) l; l >>>= 8; } return out; } }  static int decodeInt(byte[] data, int index); static BigInteger decodeBigInteger(byte[] data, int index); static RLPList decode2(byte[] msgData); static RLPElement decode2OneItem(byte[] msgData, int startPos); static DecodeResult decode(byte[] data, int pos); static byte[] encode(Object input); static byte[] encodeLength(int length, int offset); static byte[] encodeByte(byte singleByte); static byte[] encodeShort(short singleShort); static byte[] encodeInt(int singleInt); static byte[] encodeLong(long l); static byte[] encodeString(String srcString); static byte[] encodeBigInteger(BigInteger srcBigInteger); static byte[] encodeElement(byte[] srcData); static int calcElementPrefixSize(byte[] srcData); static byte[] encodeListHeader(int size); static byte[] encodeLongElementHeader(int length); static byte[] encodeList(byte[]... elements);  }### Answer:
@Test public void testEncodeDecodeDownToByte() { Long num = 1L; byte[] res = RLP.encodeLong(num); assertEquals(res.length, 1); }