add test

tests/test_utils.py

@@ -1,3 +1,4 @@
+import string
 from unittest import mock
 from urllib.parse import parse_qsl, urlparse
 
@@ -138,6 +139,17 @@ def test_wrong_device_hash(self):
         )
         self.assertFalse(validation_result)
 
+    def test_cookie_valid_characters(self):
+        user = mock.Mock()
+        user.pk = 123
+        user.password = make_password("xx")
+        allowed_characters = set(string.ascii_letters + string.digits + "-_:")
+
+        cookie_value = get_remember_device_cookie(
+            user=user, otp_device_id="SomeModel/33"
+        )
+        self.assertTrue(all(c in allowed_characters for c in cookie_value))
+
 
 class PhoneUtilsTests(UserMixin, TestCase):
     def test_get_available_phone_methods(self):