### Question:
RLP { public static byte[] encodeElement(@Nullable byte[] srcData) { if (srcData == null || srcData.length == 0) { return new byte[]{(byte) OFFSET_SHORT_ITEM}; } else if (isSingleZero(srcData)) { return srcData; } else if (srcData.length == 1 && (srcData[0] & 0xFF) < OFFSET_SHORT_ITEM) { return srcData; } else if (srcData.length < SIZE_THRESHOLD) { byte length = (byte) (OFFSET_SHORT_ITEM + srcData.length); byte[] data = Arrays.copyOf(srcData, srcData.length + 1); System.arraycopy(data, 0, data, 1, srcData.length); data[0] = length; return data; } else { int tmpLength = srcData.length; byte byteNum = 0; while (tmpLength != 0) { ++byteNum; tmpLength = tmpLength >> 8; } byte[] lenBytes = new byte[byteNum]; for (int i = 0; i < byteNum; ++i) { lenBytes[byteNum - 1 - i] = (byte) ((srcData.length >> (8 * i)) & 0xFF); } byte[] data = Arrays.copyOf(srcData, srcData.length + 1 + byteNum); System.arraycopy(data, 0, data, 1 + byteNum, srcData.length); data[0] = (byte) (OFFSET_LONG_ITEM + byteNum); System.arraycopy(lenBytes, 0, data, 1, lenBytes.length); return data; } }  static int decodeInt(byte[] data, int index); static BigInteger decodeBigInteger(byte[] data, int index); static byte[] decodeIP4Bytes(byte[] data, int index); static int getFirstListElement(byte[] payload, int pos); static int getNextElementIndex(byte[] payload, int pos); static void fullTraverse(byte[] msgData, int level, int startPos,
                                    int endPos, int levelToIndex, Queue<Integer> index); static byte getCommandCode(byte[] data); @Nonnull static ArrayList<RLPElement> decode2(@CheckForNull byte[] msgData); static RLPList decodeList(byte[] msgData); @Nullable static RLPElement decode2OneItem(@CheckForNull byte[] msgData, int startPos); @Nonnull static UscAddress parseUscAddress(@Nullable byte[] bytes); @Nonnull static Coin parseCoin(@Nullable byte[] bytes); @Nullable static Coin parseCoinNonNullZero(byte[] bytes); @Nullable static Coin parseSignedCoinNonNullZero(byte[] bytes); static Coin parseCoinNullZero(@Nullable byte[] bytes); @Nullable static BlockDifficulty parseBlockDifficulty(@Nullable byte[] bytes); 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[] encodeString(String srcString); static byte[] encodeBigInteger(BigInteger srcBigInteger); static byte[] encodeUscAddress(UscAddress addr); static byte[] encodeCoin(@Nullable Coin coin); static byte[] encodeCoinNonNullZero(@CheckForNull Coin coin); static byte[] encodeSignedCoinNonNullZero(@CheckForNull Coin coin); static byte[] encodeCoinNullZero(Coin coin); static byte[] encodeBlockDifficulty(BlockDifficulty difficulty); static byte[] encodeElement(@Nullable byte[] srcData); static byte[] encodeListHeader(int size); static byte[] encodeLongElementHeader(int length); static byte[] encodeSet(Set<ByteArrayWrapper> data); static byte[] encodeList(byte[]... elements);  }### Answer:
@Test public void testEncodeElementNull() { byte[] actuals = encodeElement((byte[]) null); assertArrayEquals(new byte[]{(byte) 0x80}, actuals); }
@Test public void testEncodeElementZero() { byte[] actuals = encodeElement(new byte[]{0x00}); assertArrayEquals(new byte[]{0x00}, actuals); }
@Test public void testEncodeElementOne() { byte[] actuals = encodeElement(new byte[]{0x01}); assertArrayEquals(new byte[]{(byte) 0x01}, actuals); }