diff --git a/.travis.yml b/.travis.yml
index c47988be8..360482c5f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,12 +1,12 @@
 language: python
-python: 2.7
+python: 3.5
 sudo: required
 dist: trusty
 env:
-  #matrix:
-  #- TOX_ENV=py27
-  #- TOX_ENV=py34
-  #- TOX_ENV=py35
+  matrix:
+  - TOX_ENV=py27
+  - TOX_ENV=py34
+  - TOX_ENV=py35
   global:
     - COVERAGE_APPEND="--append"
     - secure: cKbIgpTJ1yjKLBxpCEiT6IH7NShDWZUE+BvnrAfc+ujCsR6LyLJcKxFQmKnWryJCqg7fp82Ep2bF2oDKzanAROar2xDY1SFGbai42seYMaFCw53YPGJ6u3VNCcfT0rN9BWgE7el/m4fjcD6CRsZYKArNNJbMX8csRt3uXXCFLso=
@@ -30,15 +30,13 @@ install:
   - travis_retry python setup.py install
   - travis_retry pip install -r dev_requirements.txt
 script:
-  # XXX: For now we're only performing minimal CI checks as most tests are
-  # broken. Tests will be individually added here as they're fixed.
+  # XXX: For now we're only performing minimal lint checks as there are way
+  # too many issues. Once they're all addressed we should change this to 'make
+  # lint'.
   - make lint-minimal
-  - make test-passing
-  #- if [ -d .tox/$TOX_ENV/ ]; then cd .tox/$TOX_ENV && coverage erase; fi;
-  #- tox -e $TOX_ENV -- --ignore ethereum/tests/test_vm.py --ignore ethereum/tests/test_state.py
-  #- tox -e $TOX_ENV -- ethereum/tests/test_vm.py
-  #- tox -e $TOX_ENV -- ethereum/tests/test_state.py
-  #- coverage report --show-missing
+  - if [ -d .tox/$TOX_ENV/ ]; then cd .tox/$TOX_ENV && coverage erase; fi;
+  - tox -e $TOX_ENV -- --ignore ethereum/todo_tests
+  - coverage report --show-missing
 after_success:
   - travis_retry pip install coveralls
   - cd .tox/$TOX_ENV && coveralls
diff --git a/Makefile b/Makefile
index c1722ea76..21edb2a50 100644
--- a/Makefile
+++ b/Makefile
@@ -43,13 +43,10 @@ lint-minimal:
 	python -m flake8 --ignore=F401,F841,F811 --select=F --exclude=todo,experimental,ethash.py,ethash_utils.py ethereum
 
 test:
-	py.test --tb=no ethereum/tests/
+	py.test ethereum/tests/
 
-test-passing:
-	py.test ethereum/tests/test_abi.py ethereum/tests/test_bloom.py ethereum/tests/test_chain.py ethereum/tests/test_compress.py ethereum/tests/test_db.py ethereum/tests/test_difficulty.py ethereum/tests/test_opcodes.py ethereum/tests/test_trie_next_prev.py ethereum/tests/test_genesis.py ethereum/tests/test_serialization.py ethereum/tests/test_trie.py
-
-test-failing:
-	py.test ethereum/tests/test_blockstransactions.py ethereum/tests/test_transactions.py ethereum/tests/test_keys.py ethereum/tests/test_state.py ethereum/tests/test_contracts.py ethereum/tests/test_tester.py
+test-todo:
+	py.test --continue-on-collection-errors ethereum/todo_tests
 
 testnovm:
 	py.test --tb=no ethereum/tests/ --ignore=ethereum/tests/test_vm.py
diff --git a/ethereum/pow/chain.py b/ethereum/pow/chain.py
index b74c9d44a..d5b1a4919 100644
--- a/ethereum/pow/chain.py
+++ b/ethereum/pow/chain.py
@@ -509,7 +509,7 @@ def get_blockhashes_from_hash(self, hash, max):
 
         header = block.header
         hashes = []
-        for i in xrange(max):
+        for i in range(max):
             hash = header.prevhash
             block = self.get_block(hash)
             if block is None:
diff --git a/ethereum/slogging.py b/ethereum/slogging.py
index cad5131aa..05c7656c4 100644
--- a/ethereum/slogging.py
+++ b/ethereum/slogging.py
@@ -1,5 +1,6 @@
 import logging
 import json
+import sys
 import textwrap
 from json.encoder import JSONEncoder
 from logging import StreamHandler, Formatter, FileHandler
@@ -262,11 +263,15 @@ def getLogger(self, name):
 
 
 def _stringify_dict_keys(input_):
+    if sys.version_info.major == 2:
+        longType = long # NOQA
+    else:
+        longType = int
     if isinstance(input_, dict):
         res = {}
         for k, v in input_.items():
             v = _stringify_dict_keys(v)
-            if not isinstance(k, (int, long, bool, None.__class__)):
+            if not isinstance(k, (int, longType, bool, None.__class__)):
                 k = str(k)
             res[k] = v
     elif isinstance(input_, (list, tuple)):
diff --git a/ethereum/utils.py b/ethereum/utils.py
index 69867ca0c..e9750966e 100644
--- a/ethereum/utils.py
+++ b/ethereum/utils.py
@@ -35,9 +35,8 @@ def int_to_big_endian(x): return big_endian_int.serialize(x)
 SECP256K1P = 2**256 - 4294968273
 
 if sys.version_info.major == 2:
-    def is_numeric(x): return isinstance(x, (int, long))
-
-    def is_string(x): return isinstance(x, (str, unicode))
+    is_numeric = lambda x: isinstance(x, (int, long))  # NOQA
+    is_string = lambda x: isinstance(x, (str, unicode)) # NOQA
 
     def to_string(value):
         return str(value)
@@ -49,7 +48,7 @@ def int_to_bytes(value):
 
     def to_string_for_regexp(value):
         return str(value)
-    unicode = unicode
+    unicode = unicode # NOQA
 
     def bytearray_to_bytestr(value):
         return bytes(''.join(chr(c) for c in value))