adding test around update statement ttls

cqlengine/models.py

@@ -69,6 +69,7 @@ class QuerySetDescriptor(object):
         """
         raise NotImplementedError
 
+
 class TTLDescriptor(object):
     """
     returns a query set descriptor

cqlengine/tests/statements/test_update_statement.py

@@ -24,3 +24,10 @@ class UpdateStatementTests(TestCase):
         us.add_assignment_clause(AssignmentClause('c', 'd'))
         us.add_where_clause(WhereClause('a', EqualsOperator(), 'x'))
         self.assertEqual(us.get_context(), {0: 'b', 1: 'd', 2: 'x'})
+
+    def test_additional_rendering(self):
+        us = UpdateStatement('table', ttl=60)
+        us.add_assignment_clause(AssignmentClause('a', 'b'))
+        us.add_where_clause(WhereClause('a', EqualsOperator(), 'x'))
+        self.assertIn('USING TTL 60', unicode(us))
+