Add test for deleted users.

tests/test_serializers.py

@@ -6,6 +6,7 @@
 from django.contrib.auth import get_user_model
 from django.test import TestCase
 from rest_framework import exceptions as drf_exceptions
+from django.core import exceptions as django_exceptions
 
 from rest_framework_simplejwt.exceptions import TokenError
 from rest_framework_simplejwt.serializers import (
@@ -256,6 +257,18 @@ def setUp(self):
             password=self.password,
         )
 
+    def test_it_should_raise_error_for_deleted_users(self):
+        refresh = RefreshToken.for_user(self.user)
+        self.user.delete()
+
+        s = TokenRefreshSerializer(data={"refresh": str(refresh)})
+
+        with self.assertRaises(django_exceptions.ObjectDoesNotExist) as e:
+            s.is_valid()
+
+        self.assertIn("does not exist", str(e.exception))
+
+
     def test_it_should_raise_error_for_inactive_users(self):
         refresh = RefreshToken.for_user(self.user)
         self.user.is_active = False