More test coverage around strict and timedelta addition

testfixtures/tests/test_date.py

@@ -1,4 +1,4 @@
-from datetime import date as d, timedelta
+from datetime import date as d, timedelta, date
 from time import strptime
 from typing import cast, Type
 
@@ -300,3 +300,15 @@ def test_tick_with_timedelta_instance(self):
     def test_old_import(self):
         from testfixtures import test_date
         assert test_date is mock_date
+
+    def test_add_timedelta_not_strict(self):
+        mock_class = mock_date()
+        value = mock_class.today() + timedelta(days=1)
+        assert isinstance(value, date)
+        assert type(value) is date
+
+    def test_add_timedelta_strict(self):
+        mock_class = mock_date(strict=True)
+        value = mock_class.today() + timedelta(days=1)
+        assert isinstance(value, date)
+        assert type(value) is mock_class

testfixtures/tests/test_datetime.py

@@ -1,4 +1,4 @@
-from datetime import date
+from datetime import date, datetime
 from datetime import datetime as d
 from datetime import timedelta
 from datetime import tzinfo
@@ -433,3 +433,15 @@ def test_tick_with_timedelta_instance(self):
     def test_old_import(self):
         from testfixtures import test_datetime
         assert test_datetime is mock_datetime
+
+    def test_add_timedelta_not_strict(self):
+        mock_class = mock_datetime()
+        value = mock_class.now() + timedelta(seconds=10)
+        assert isinstance(value, datetime)
+        assert type(value) is datetime
+
+    def test_add_timedelta_strict(self):
+        mock_class = mock_datetime(strict=True)
+        value = mock_class.now() + timedelta(seconds=10)
+        assert isinstance(value, datetime)
+        assert type(value) is mock_class