1 files changed, 10 insertions, 0 deletions
diff --git a/Lib/test/test_selectors.py b/Lib/test/test_selectors.py
index fd0481d..c64c87a 100644
--- a/Lib/test/test_selectors.py
+++ b/Lib/test/test_selectors.py
@@ -6,6 +6,7 @@ import socket
 from test import support
 from time import sleep
 import unittest
+import unittest.mock
 try:
     from time import monotonic as time
 except ImportError:
@@ -124,6 +125,15 @@ class BaseSelectorTestCase(unittest.TestCase):
         # modify unknown file obj
         self.assertRaises(KeyError, s.modify, 999999, selectors.EVENT_READ)
 
+        # modify use a shortcut
+        d3 = object()
+        s.register = unittest.mock.Mock()
+        s.unregister = unittest.mock.Mock()
+
+        s.modify(rd, selectors.EVENT_READ, d3)
+        self.assertFalse(s.register.called)
+        self.assertFalse(s.unregister.called)
+
     def test_close(self):
         s = self.SELECTOR()
         self.addCleanup(s.close)