[3.11] gh-100871: Improve copy module tests (GH-100872) (#100976)

(cherry picked from commit 729ab9b622)

Co-authored-by: Nikita Sobolev <mail@sobolevn.me>

Lib/test/test_slice.py

@@ -5,6 +5,7 @@ import operator
 import sys
 import unittest
 import weakref
+import copy
 
 from pickle import loads, dumps
 from test import support
@@ -242,6 +243,41 @@ class SliceTest(unittest.TestCase):
             self.assertEqual(s.indices(15), t.indices(15))
             self.assertNotEqual(id(s), id(t))
 
+    def test_copy(self):
+        s = slice(1, 10)
+        c = copy.copy(s)
+        self.assertIs(s, c)
+
+        s = slice(1, 10, 2)
+        c = copy.copy(s)
+        self.assertIs(s, c)
+
+        # Corner case for mutable indices:
+        s = slice([1, 2], [3, 4], [5, 6])
+        c = copy.copy(s)
+        self.assertIs(s, c)
+        self.assertIs(s.start, c.start)
+        self.assertIs(s.stop, c.stop)
+        self.assertIs(s.step, c.step)
+
+    def test_deepcopy(self):
+        s = slice(1, 10)
+        c = copy.deepcopy(s)
+        self.assertEqual(s, c)
+
+        s = slice(1, 10, 2)
+        c = copy.deepcopy(s)
+        self.assertEqual(s, c)
+
+        # Corner case for mutable indices:
+        s = slice([1, 2], [3, 4], [5, 6])
+        c = copy.deepcopy(s)
+        self.assertIsNot(s, c)
+        self.assertEqual(s, c)
+        self.assertIsNot(s.start, c.start)
+        self.assertIsNot(s.stop, c.stop)
+        self.assertIsNot(s.step, c.step)
+
     def test_cycle(self):
         class myobj(): pass
         o = myobj()