Closes #15514: Correct __sizeof__ support for cpu_set
diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index f0ad92f..0ea696b 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -1008,6 +1008,12 @@
         self.assertIs(b, l)
         self.assertEqual(l.count(), 3)
 
+    @requires_sched_affinity
+    @support.cpython_only
+    def test_cpu_set_sizeof(self):
+        self.assertGreater(sys.getsizeof(posix.cpu_set(1000)),
+                           sys.getsizeof(posix.cpu_set(1)))
+
     def test_rtld_constants(self):
         # check presence of major RTLD_* constants
         posix.RTLD_LAZY