Add tests to prevent regression in MonitorField behaviour if we filter out deferred fields in _save_initial

model_utils/tests/tests.py

@@ -2,6 +2,8 @@ from __future__ import unicode_literals
 
 from datetime import datetime, timedelta
 
+from freezegun import freeze_time
+
 try:
     from unittest import skipUnless
 except ImportError: # Python 2.6
@@ -261,6 +263,13 @@ class MonitorDoubleFieldTests(TestCase):
         # Only monitored fields passed to defer() are failing
         list(DoubleMonitored.objects.defer('name'))
 
+    def test_monitor_still_works_with_deferred_fields_filtered_out_of_save_initial(self):
+        obj = DoubleMonitored.objects.defer('name').get(name='Charlie')
+        with freeze_time("2016-12-01"):
+            obj.name = 'Charlie2'
+            obj.save()
+        self.assertEqual(obj.name_changed, datetime(2016, 12, 1))
+
 
 class StatusFieldTests(TestCase):
 

tox.ini

@@ -25,5 +25,6 @@ deps =
     django110: Django>=1.10,<1.11
     django_trunk: https://github.com/django/django/tarball/master
     django{14,15,16}: South==1.0.2
+    freezegun == 0.3.8
 
 commands = coverage run -a setup.py test