Add a test.

Author: serhiy-storchaka

Lib/test/test_curses.py

@@ -8,7 +8,8 @@
 from unittest.mock import MagicMock
 
 from test.support import (requires, verbose, SaveSignals, cpython_only,
-                          check_disallow_instantiation, MISSING_C_DOCSTRINGS)
+                          check_disallow_instantiation, MISSING_C_DOCSTRINGS,
+                          gc_collect)
 from test.support.import_helper import import_module
 
 # Optionally test curses module.  This currently requires that the
@@ -181,6 +182,14 @@ def test_create_windows(self):
         self.assertEqual(win3.getparyx(), (2, 1))
         self.assertEqual(win3.getmaxyx(), (6, 11))
 
+    def test_subwindows_references(self):
+        win = curses.newwin(5, 10)
+        win2 = win.subwin(3, 7)
+        del win
+        gc_collect()
+        del win2
+        gc_collect()
+
     def test_move_cursor(self):
         stdscr = self.stdscr
         win = stdscr.subwin(10, 15, 2, 5)