test: add more tests for has_value_changed

frappe/model/document.py

@@ -4,7 +4,6 @@ import hashlib
 import json
 import time
 from collections.abc import Generator, Iterable
-from datetime import date, datetime, timedelta
 from typing import TYPE_CHECKING, Any, Optional
 
 from werkzeug.exceptions import NotFound
@@ -456,6 +455,8 @@ class Document(BaseDocument):
 
 	def has_value_changed(self, fieldname):
 		"""Return True if value has changed before and after saving."""
+		from datetime import date, datetime, timedelta
+
 		previous = self.get_doc_before_save()
 
 		if not previous:

frappe/tests/test_document.py

@@ -101,8 +101,13 @@ class TestDocument(FrappeTestCase):
 	def test_value_changed(self):
 		d = self.test_insert()
 		d.subject = "subject changed again"
-		d.save()
+		d.load_doc_before_save()
+		d.update_modified()
+
 		self.assertTrue(d.has_value_changed("subject"))
+		self.assertTrue(d.has_value_changed("modified"))
+
+		self.assertFalse(d.has_value_changed("creation"))
 		self.assertFalse(d.has_value_changed("event_type"))
 
 	def test_mandatory(self):