Successfully tested

test/helpers/hashMessage.js

@@ -0,0 +1,8 @@
+import utils from 'ethereumjs-util';
+
+// Hash and add same prefix to the hash that testrpc use.
+module.exports = function (message) {
+  const messageHex = Buffer.from(utils.sha3(message).toString('hex'), 'hex');
+  const prefix = utils.toBuffer('\u0019Ethereum Signed Message:\n' + messageHex.length.toString());
+  return utils.bufferToHex(utils.sha3(Buffer.concat([prefix, messageHex])));
+};