tx.sign(cowPrivKey);
byte[] postTxState = Hex.decode("7fa5bd00f6e03b5a5718560f1e25179b227167585a3c3da06a48f554365fb527");
byte[] cumGas = Hex.decode("0272");
TransactionReceipt tr = new TransactionReceipt(tx, postTxState, cumGas);
Trie trie = new TrieImpl(new MockDB());
trie.update(RLP.encodeInt(0), tr.getEncoded());
String txTrieRoot = Hex.toHexString(trie.getRootHash());
assertEquals(expected, txTrieRoot);
}