diff --git a/tests/__init__.py b/tests/__init__.py
index fc99f6b6..d75f2e89 100644
--- a/tests/__init__.py
+++ b/tests/__init__.py
@@ -23,3 +23,5 @@
 ``python setup.py test``).
 
 """
+import warnings
+warnings.simplefilter('error')
diff --git a/tests/test_filtering.py b/tests/test_filtering.py
index 0c3efe59..6ad71e0a 100644
--- a/tests/test_filtering.py
+++ b/tests/test_filtering.py
@@ -14,6 +14,7 @@
 from datetime import datetime
 from datetime import time
 from unittest2 import skip
+import sys
 
 # This import is unused but is required for testing on PyPy. CPython can
 # use psycopg2, but PyPy can only use psycopg2cffi.
@@ -40,6 +41,11 @@
 from .helpers import loads
 from .helpers import ManagerTestBase
 
+if sys.version_info < (3, 0):
+    to_string = unicode
+else:
+    to_string = str
+
 
 #: The PostgreSQL class used to create a temporary database for testing.
 #:
@@ -949,7 +955,7 @@ def test_to_many_filter_by_relation(self):
         self.session.add(article)
         for i in range(1, 3):
             comment = self.Comment(id=i)
-            tag = self.Tag(name=str(i))
+            tag = self.Tag(name=to_string(i))
             comment.article = article
             comment.tag = tag
             self.session.add_all([comment, tag])
diff --git a/tests/test_validation.py b/tests/test_validation.py
index beca25de..7c7d3044 100644
--- a/tests/test_validation.py
+++ b/tests/test_validation.py
@@ -301,12 +301,9 @@ def test_create_absent(self):
         """
         data = dict(data=dict(type='person'))
         response = self.app.post('/api/person', data=dumps(data))
-        assert response.status_code == 400
-        document = loads(response.data)
-        errors = document['errors']
-        error = errors[0]
-        assert 'validation' in error['title'].lower()
-        assert 'email' in error['detail'].lower()
+        print(response)
+        print(response.data)
+        check_sole_error(response, 400, ['validation', 'email'])
         # Check that the person was not created.
         assert self.session.query(self.Person).count() == 0
 
@@ -321,12 +318,7 @@ def test_create_invalid(self):
                      }
                 }
         response = self.app.post('/api/person', data=dumps(data))
-        assert response.status_code == 400
-        document = loads(response.data)
-        errors = document['errors']
-        error = errors[0]
-        assert 'validation' in error['title'].lower()
-        assert 'email' in error['detail'].lower()
+        check_sole_error(response, 400, ['validation', 'email'])
         # Check that the person was not created.
         assert self.session.query(self.Person).count() == 0
 
@@ -363,11 +355,6 @@ def test_update_invalid(self):
                      }
                 }
         response = self.app.patch('/api/person/1', data=dumps(data))
-        assert response.status_code == 400
-        document = loads(response.data)
-        errors = document['errors']
-        error = errors[0]
-        assert 'validation' in error['title'].lower()
-        assert 'email' in error['detail'].lower()
+        check_sole_error(response, 400, ['validation', 'email'])
         # Check that the person was not updated.
         assert person.email == u'example@example.com'