diff --git a/Opcode.js b/Opcode.js
index 5ae4bee82..44f693ff0 100644
--- a/Opcode.js
+++ b/Opcode.js
@@ -155,4 +155,14 @@ for (var k in Opcode.map) {
   }
 }
 
+Opcode.asList = function() {
+  var keys = [];
+  for (var prop in Opcode.map) {
+    if (Opcode.map.hasOwnProperty(prop)) {
+      keys.push(prop);
+    }
+  }
+  return keys;
+};
+
 module.exports = require('soop')(Opcode);
diff --git a/Script.js b/Script.js
index ada391de6..95f522c2c 100644
--- a/Script.js
+++ b/Script.js
@@ -265,6 +265,8 @@ Script.prototype.getBuffer = function() {
   return this.buffer;
 };
 
+Script.prototype.serialize = Script.prototype.getBuffer;
+
 Script.prototype.getStringContent = function(truncate, maxEl) {
   if (truncate === null) {
     truncate = true;
diff --git a/test/test.Opcode.js b/test/test.Opcode.js
index 235f26cb9..9a0ea663e 100644
--- a/test/test.Opcode.js
+++ b/test/test.Opcode.js
@@ -17,13 +17,13 @@ describe('Opcode', function() {
     should.exist(Opcode);
   });
   it('should be able to create instance', function() {
-    var oc = new Opcode();
+    var oc = new Opcode(81);
     should.exist(oc);
   });
   it('should be able to create some constants', function() {
     // TODO: test works in node but not in browser
     for (var i in Opcode.map) {
-      eval('var '+i + ' = ' + Opcode.map[i] + ';');
+      eval('var ' + i + ' = ' + Opcode.map[i] + ';');
     }
     should.exist(OP_VER);
     should.exist(OP_HASH160);
@@ -31,11 +31,10 @@ describe('Opcode', function() {
     should.exist(OP_EQUALVERIFY);
     should.exist(OP_CHECKSIG);
     should.exist(OP_CHECKMULTISIG);
-
+  });
+  it('#asList should work', function() {
+    var list = Opcode.asList();
+    (typeof(list[0])).should.equal('string');
+    list.length.should.equal(116);
   });
 });
-
-
-
-
-
diff --git a/test/test.sighash.js b/test/test.sighash.js
new file mode 100644
index 000000000..8ef6d1fc7
--- /dev/null
+++ b/test/test.sighash.js
@@ -0,0 +1,91 @@
+'use strict';
+
+// inspired in bitcoin core test:
+// https://github.com/bitcoin/bitcoin/blob/7d49a9173ab636d118c2a81fc3c3562192e7813a/src/test/sighash_tests.cpp
+
+var chai = chai || require('chai');
+var should = chai.should();
+var bitcore = bitcore || require('../bitcore');
+var Transaction = bitcore.Transaction;
+var Script = bitcore.Script;
+var Opcode = bitcore.Opcode;
+
+var randInt = function(low, high) {
+  return Math.floor(Math.random() * (high - low + 1) + low);
+};
+var randUIntN = function(nBits) {
+  return randInt(0, Math.pow(2, nBits));
+};
+var randUInt32 = function() {
+  return randUIntN(32);
+};
+var randBool = function() {
+  return Math.random() < 0.5;
+};
+var hexAlphabet = '0123456789abcdef';
+var randHex = function() {
+  return hexAlphabet[randInt(0, 15)];
+};
+var randHexN = function(n) {
+  var s = '';
+  while (n--) {
+    s += randHex();
+  }
+  return s;
+};
+var randTxHash = function() {
+  return randHexN(64);
+};
+var randPick = function(list) {
+  return list[randInt(0, list.length-1)];
+};
+
+
+var opList = Opcode.asList();
+
+var randomScript = function() {
+  var s = new Script();
+  var ops = randInt(0,10);
+  for (var i=0; i<ops; i++) {
+    var op = randPick(opList);
+    s.writeOp(Opcode.map[op]);
+  }
+  return s;
+};
+
+var randomTx = function(single) {
+  var tx = new Transaction({
+    version: randUInt32(),
+    lock_time: randBool() ? randUInt32() : 0
+  });
+  var insN = randInt(1, 5);
+  var outsN = single ? insN : randInt(1, 5);
+  for (var i = 0; i < insN; i++) {
+    var txin = new Transaction.In({
+      oTxHash: randTxHash(),
+      oIndex: randInt(0, 4),
+      script: randomScript().serialize(),
+      sequence: randBool() ? randUInt32() : 0xffffffff
+    });
+    tx.ins.push(txin);
+  }
+  for (i = 0; i < outsN; i++) {
+    var txout = Transaction.Out({
+      value: randInt(0,100000000),
+      script: randomScript().serialize()
+    });
+    tx.outs.push(txout);
+  }
+  return tx;
+};
+
+describe('Transaction sighash (#hashForSignature)', function() {
+  for (var i = 0; i < 10; i++) {
+    it('should hash correctly random tx #'+(i+1), function() {
+      var tx = randomTx();
+      console.log(tx);
+      tx.hashForSignature(script, inIndex, hashType);
+      return;
+    });
+  }
+});