Unroll subtests.

Author: WaVEV

tests/model_fields_/test_objectidfield.py

@@ -17,14 +17,18 @@ def test_get_internal_type(self):
         f = ObjectIdField()
         self.assertEqual(f.get_internal_type(), "ObjectIdField")
 
-    def test_to_python(self):
-        f = ObjectIdField()
-        expected = ObjectId("1" * 24)
-        for value in ["1" * 24, ObjectId("1" * 24)]:
-            with self.subTest(value=value):
-                self.assertEqual(f.to_python(value), expected)
-        with self.subTest(value=None):
-            self.assertIsNone(f.to_python(None))
+    def test_to_python_string(self):
+        base_string = "1" * 24
+        expected = ObjectId(base_string)
+        self.assertEqual(ObjectIdField().to_python(base_string), expected)
+
+    def test_to_python_objectid(self):
+        base_string = "1" * 24
+        expected = ObjectId(base_string)
+        self.assertEqual(ObjectIdField().to_python(expected), expected)
+
+    def test_to_python_null_value(self):
+        self.assertIsNone(ObjectIdField().to_python(None))
 
     def test_to_python_invalid_value(self):
         for invalid_value in ["None", {}, []]: