test: contextmanager to change settings

erpnext/tests/utils.py

@@ -1,7 +1,8 @@
-# Copyright (c) 2015, Frappe Technologies Pvt. Ltd. and Contributors
+# Copyright (c) 2021, Frappe Technologies Pvt. Ltd. and Contributors
 # License: GNU General Public License v3. See license.txt
 
-from __future__ import unicode_literals
+import copy
+from contextlib import contextmanager
 
 import frappe
 
@@ -41,3 +42,38 @@ def create_test_contact_and_address():
 	contact.add_email("test_contact_customer@example.com", is_primary=True)
 	contact.add_phone("+91 0000000000", is_primary_phone=True)
 	contact.insert()
+
+
+@contextmanager
+def change_settings(doctype, settings_dict):
+	""" A context manager to ensure that settings are changed before running
+	function and restored after running it regardless of exceptions occured.
+	This is useful in tests where you want to make changes in a function but
+	don't retain those changes.
+	import and use as decorator to cover full function or using `with` statement.
+
+	example:
+	@change_settings("Stock Settings", {"item_naming_by": "Naming Series"})
+	def test_case(self):
+		...
+	"""
+
+	try:
+		settings = frappe.get_doc(doctype)
+		# remember setting
+		previous_settings = copy.deepcopy(settings_dict)
+		for key in previous_settings:
+			previous_settings[key] = getattr(settings, key)
+
+		# change setting
+		for key, value in settings_dict.items():
+			setattr(settings, key, value)
+		settings.save()
+		yield # yield control to calling function
+
+	finally:
+		# restore settings
+		settings = frappe.get_doc(doctype)
+		for key, value in previous_settings.items():
+			setattr(settings, key, value)
+		settings.save()