Update ExceptionGroup tests for new repr and add mutation test

Author: dr-carlos

Lib/test/test_exception_group.py

@@ -131,67 +131,82 @@ class MyBEG(BaseExceptionGroup):
 
 class StrAndReprTests(unittest.TestCase):
     def test_ExceptionGroup(self):
+        eg_excs = [ValueError(1), TypeError(2)]
         eg = BaseExceptionGroup(
-            'flat', [ValueError(1), TypeError(2)])
+            'flat', eg_excs)
 
         self.assertEqual(str(eg), "flat (2 sub-exceptions)")
         self.assertEqual(repr(eg),
-            "ExceptionGroup('flat', [ValueError(1), TypeError(2)])")
+            "ExceptionGroup('flat', (ValueError(1), TypeError(2)))")
+
+        # Mutate the list of exceptions passed to BaseExceptionGroup.
+        # This shouldn't change the EG's functionality, nor its repr.
+        eg_excs.clear()
 
         eg = BaseExceptionGroup(
             'nested', [eg, ValueError(1), eg, TypeError(2)])
 
         self.assertEqual(str(eg), "nested (4 sub-exceptions)")
         self.assertEqual(repr(eg),
             "ExceptionGroup('nested', "
-                "[ExceptionGroup('flat', "
-                    "[ValueError(1), TypeError(2)]), "
+                "(ExceptionGroup('flat', "
+                    "(ValueError(1), TypeError(2))), "
                  "ValueError(1), "
                  "ExceptionGroup('flat', "
-                    "[ValueError(1), TypeError(2)]), TypeError(2)])")
+                    "(ValueError(1), TypeError(2))), TypeError(2)))")
 
     def test_BaseExceptionGroup(self):
+        eg_excs = [ValueError(1), KeyboardInterrupt(2)]
         eg = BaseExceptionGroup(
-            'flat', [ValueError(1), KeyboardInterrupt(2)])
+            'flat', eg_excs)
 
         self.assertEqual(str(eg), "flat (2 sub-exceptions)")
         self.assertEqual(repr(eg),
             "BaseExceptionGroup("
                 "'flat', "
-                "[ValueError(1), KeyboardInterrupt(2)])")
+                "(ValueError(1), KeyboardInterrupt(2)))")
+
+        # Mutate the list of exceptions passed to BaseExceptionGroup.
+        # This shouldn't change the EG's functionality, nor its repr.
+        eg_excs.clear()
 
         eg = BaseExceptionGroup(
             'nested', [eg, ValueError(1), eg])
 
         self.assertEqual(str(eg), "nested (3 sub-exceptions)")
         self.assertEqual(repr(eg),
             "BaseExceptionGroup('nested', "
-                "[BaseExceptionGroup('flat', "
-                    "[ValueError(1), KeyboardInterrupt(2)]), "
+                "(BaseExceptionGroup('flat', "
+                    "(ValueError(1), KeyboardInterrupt(2))), "
                 "ValueError(1), "
                 "BaseExceptionGroup('flat', "
-                    "[ValueError(1), KeyboardInterrupt(2)])])")
+                    "(ValueError(1), KeyboardInterrupt(2)))))")
 
     def test_custom_exception(self):
         class MyEG(ExceptionGroup):
             pass
 
+        eg_excs = [ValueError(1), TypeError(2)]
         eg = MyEG(
-            'flat', [ValueError(1), TypeError(2)])
+            'flat', eg_excs)
 
         self.assertEqual(str(eg), "flat (2 sub-exceptions)")
-        self.assertEqual(repr(eg), "MyEG('flat', [ValueError(1), TypeError(2)])")
+        self.assertEqual(repr(eg), "MyEG('flat', (ValueError(1), TypeError(2)))")
+
+        # Mutate the list of exceptions passed to BaseExceptionGroup.
+        # This shouldn't change the EG's functionality, nor its repr.
+        eg_excs.clear()
 
         eg = MyEG(
             'nested', [eg, ValueError(1), eg, TypeError(2)])
 
         self.assertEqual(str(eg), "nested (4 sub-exceptions)")
         self.assertEqual(repr(eg), (
                  "MyEG('nested', "
-                     "[MyEG('flat', [ValueError(1), TypeError(2)]), "
+                     "(MyEG('flat', (ValueError(1), TypeError(2))), "
                       "ValueError(1), "
-                      "MyEG('flat', [ValueError(1), TypeError(2)]), "
-                      "TypeError(2)])"))
+                      "MyEG('flat', (ValueError(1), TypeError(2))), "
+                      "TypeError(2)))"))
 
 
 def create_simple_eg():