Adds common includes and tests.
diff --git a/tests/test_common.py b/tests/test_common.py
index bad24f8..9980b15 100644
--- a/tests/test_common.py
+++ b/tests/test_common.py
@@ -34,6 +34,9 @@
         self.assertRaises(TypeError, byte_size, None)
 
 class Test_bit_size(unittest2.TestCase):
+    def test_zero(self):
+        self.assertEqual(bit_size(0), 0)
+
     def test_values(self):
         self.assertEqual(bit_size(1023), 10)
         self.assertEqual(bit_size(1024), 11)