Additional test checking Zone threshold defaults to None

tests/config/zone-threshold.yaml

@@ -26,3 +26,9 @@ zones:
     - in
     targets:
     - dump
+
+  defaultthresholds.tests.:
+    sources:
+    - in
+    targets:
+    - dump

tests/test_octodns_manager.py

@@ -1311,6 +1311,12 @@ class TestManager(TestCase):
             self.assertEqual(0.02, subzone.update_pcent_threshold)
             self.assertEqual(0.01, subzone.delete_pcent_threshold)
 
+            # test default of None to ensure Provider precedence
+            zone_with_defaults = manager.get_zone('defaultthresholds.tests.')
+
+            self.assertIsNone(zone_with_defaults.update_pcent_threshold)
+            self.assertIsNone(zone_with_defaults.delete_pcent_threshold)
+
 
 class TestMainThreadExecutor(TestCase):
     def test_success(self):