### Question:
TransactionEncoder { public static byte[] signMessage(RawTransaction rawTransaction, Credentials credentials) { byte[] encodedTransaction = encode(rawTransaction); Sign.SignatureData signatureData = Sign.signMessage( encodedTransaction, credentials.getEcKeyPair()); return encode(rawTransaction, signatureData); }  static byte[] signMessage(RawTransaction rawTransaction, Credentials credentials); static byte[] signMessage(
            RawTransaction rawTransaction, long chainId, Credentials credentials); static Sign.SignatureData createEip155SignatureData(
            Sign.SignatureData signatureData, long chainId); static byte[] encode(RawTransaction rawTransaction); static byte[] encode(RawTransaction rawTransaction, long chainId);  }### Answer:
@Test public void testEip155Transaction() { Credentials credentials = Credentials.create("0x4646464646464646464646464646464646464646464646464646464646464646"); assertThat(TransactionEncoder.signMessage(createEip155RawTransaction(), NetworkParameters.MainNetParams.getChainId(), credentials), is(Numeric.hexStringToByteArray("0xf86d098504a817c8008252089433c98f20dd73d7bb1d533c4aa3371f2b30c6ebde880de0b6b3a76400008081eba0767f0f54ed49b6078961214a388c73f1e68b885c02cd800b5e3da81b1bf3eba3a048e6fc2d15ca4a8511bb68c3f53e014ca2f7362e98b0a94dc5771708e854bd90"))); }