diff --git a/.travis.yml b/.travis.yml
new file mode 100644
index 0000000..6b30cb1
--- /dev/null
+++ b/.travis.yml
@@ -0,0 +1,16 @@
+language: python
+python:
+  - "3.5"
+env:
+  matrix:
+    - TOX_ENV=py27
+    - TOX_ENV=py34
+    - TOX_ENV=py35
+cache: pip
+install:
+  - "travis_retry pip install setuptools --upgrade"
+  - "travis_retry pip install tox"
+script:
+  - tox -e $TOX_ENV
+after_script:
+  - cat .tox/$TOX_ENV/log/*.log
diff --git a/README.md b/README.md
index 03dfcc1..d0a26b8 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,26 @@
-Installation:
+# Installation:
 
-```make && sudo make install```
+`make && sudo make install`
+
+
+# Testing
+
+Testing is done using `pytest` and `tox`.
+
+```bash
+$ pip install tox -r requirements-dev.txt
+```
+
+
+To run the test suite in your current python version:
+
+```bash
+$ py.test
+```
+
+
+To run the full test suite across all supported python versions:
+
+```bash
+$ tox
+```
diff --git a/examples/cyberdyne/market.se b/examples/cyberdyne/market.se
index ec11925..f29763e 100644
--- a/examples/cyberdyne/market.se
+++ b/examples/cyberdyne/market.se
@@ -13,8 +13,8 @@ data current_epoch
 data price
 data volume
 
-extern heap: [pop:_:i, push:i:_, size:_:i, top:_:i]
-extern subcurrency: [balance:i:i, change_ownership:i:_, issue:ii:_, last_tx:_:a, send:ii:i]
+extern heap: [pop:[]:int256, push:[int256]:_, set_owner:[int256]:_, size:[]:int256, top:[]:int256]
+extern subcurrency: [balance:[int256]:int256, change_ownership:[int256]:_, issue:[int256,int256]:_, last_tx:[]:int256[], send:[int256,int256]:int256]
 
 # Initialize with [ buy_heap, sell_heap, first_subcurrency, second_subcurrency ]
 def init_market(buy_heap, sell_heap, first_subcurrency, second_subcurrency):
diff --git a/examples/cyberdyne/test/test_market.py b/examples/cyberdyne/test/test_market.py
index 0abbc91..d237283 100644
--- a/examples/cyberdyne/test/test_market.py
+++ b/examples/cyberdyne/test/test_market.py
@@ -3,14 +3,14 @@
 from serpent import mk_full_signature
 
 def decode_buy_order(order):
-    buyprice = -(order / 2**208)
-    buyfcvalue = (order / 2**160) % 2**48
+    buyprice = -(order // 2**208)
+    buyfcvalue = (order // 2**160) % 2**48
     buyer = order % 2**160
     return (buyprice, buyfcvalue, buyer)
 
 def decode_sell_order(order):
-    sellprice = order / 2**208
-    sellscvalue = (order / 2**160) % 2**48
+    sellprice = order // 2**208
+    sellscvalue = (order // 2**160) % 2**48
     seller = order % 2**160
     return (sellprice, sellscvalue, seller)
 
diff --git a/requirements-dev.txt b/requirements-dev.txt
new file mode 100644
index 0000000..f161ac1
--- /dev/null
+++ b/requirements-dev.txt
@@ -0,0 +1,3 @@
+pytest==2.9.2
+#ethereum==1.3.6
+https://github.com/ethereum/pyethereum/tarball/develop
diff --git a/serpent.py b/serpent.py
index a05d35a..3b6d7ff 100644
--- a/serpent.py
+++ b/serpent.py
@@ -7,6 +7,12 @@
 
 VERSION = '2.0.2'
 
+if sys.version_info.major == 2:
+    str_types = (bytes, str, unicode)
+else:
+    str_types = (bytes, str)
+
+
 def strtobytes(x):
     return x.encode('ascii') if isinstance(x, str) else x
 
@@ -81,7 +87,7 @@ def takelist(x):
 def pre_transform(code, params):
     code2 = ''
     for k, v in params.items():
-        if isinstance(v, (str, bytes, unicode)):
+        if isinstance(v, str_types):
             v = '"' + str(v) + '"'
         code2 += 'macro $%s:\n    %s\n' % (k, v)
     if os.path.exists(code):
@@ -102,8 +108,8 @@ def pre_transform(code, params):
 serialize = lambda x: pyext.serialize(takelist(strtobytes(x)))
 deserialize = lambda x: map(node, pyext.deserialize(x))
 mk_signature = lambda code, **kwargs: pyext.mk_signature(strtobytes(pre_transform(code, kwargs)))
-mk_full_signature = lambda code, **kwargs: json.loads(pyext.mk_full_signature(strtobytes(pre_transform(code, kwargs))))
-mk_contract_info_decl = lambda code, **kwargs: json.loads(pyext.mk_contract_info_decl(strtobytes(pre_transform(code, kwargs))))
+mk_full_signature = lambda code, **kwargs: json.loads(bytestostr(pyext.mk_full_signature(strtobytes(pre_transform(code, kwargs)))))
+mk_contract_info_decl = lambda code, **kwargs: json.loads(bytestostr(pyext.mk_contract_info_decl(strtobytes(pre_transform(code, kwargs)))))
 get_prefix = lambda x: pyext.get_prefix(strtobytes(x)) % 2**32
 
 if sys.version_info.major == 2:
@@ -222,7 +228,7 @@ def main():
             kwargs['source'] = 'cmdline'
         o = globals()[cmd](*args, **kwargs)
         if cmd in ['mk_full_signature', 'mk_contract_info_decl']:
-            print json.dumps(o)
+            print(json.dumps(o))
         elif isinstance(o, (Token, Astnode, dict, list)):
             print(repr(o))
         elif cmd in ['mk_full_signature', 'get_prefix']:
diff --git a/setup.py b/setup.py
index 24ce343..ad08aca 100644
--- a/setup.py
+++ b/setup.py
@@ -43,5 +43,13 @@
         'console_scripts': [
             'serpent = serpent:main',
         ],
-    }
-    ),
+    },
+    classifiers=[
+        'Intended Audience :: Developers',
+        'Programming Language :: Python :: 2',
+        'Programming Language :: Python :: 2.7',
+        'Programming Language :: Python :: 3',
+        'Programming Language :: Python :: 3.4',
+        'Programming Language :: Python :: 3.5',
+    ],
+)
diff --git a/tox.ini b/tox.ini
new file mode 100644
index 0000000..5701ef7
--- /dev/null
+++ b/tox.ini
@@ -0,0 +1,10 @@
+[tox]
+envlist=
+    py27,
+    py34,
+    py35
+
+[testenv]
+commands=py.test --tb native {posargs:.}
+deps =
+    -r{toxinidir}/requirements-dev.txt