bpo-29839: Raise ValueError rather than OverflowError in len() for negative values. (#701)

1 files changed, 8 insertions, 0 deletions

diff --git a/Lib/test/test_builtin.py b/Lib/test/test_builtin.py
index d2420e9dda..6613ca3a8c 100644
--- a/Lib/test/test_builtin.py
+++ b/Lib/test/test_builtin.py
@@ -770,10 +770,18 @@ class BuiltinTest(unittest.TestCase):
             def __len__(self):
                 return 4.5
         self.assertRaises(TypeError, len, FloatLen())
+        class NegativeLen:
+            def __len__(self):
+                return -10
+        self.assertRaises(ValueError, len, NegativeLen())
         class HugeLen:
             def __len__(self):
                 return sys.maxsize + 1
         self.assertRaises(OverflowError, len, HugeLen())
+        class HugeNegativeLen:
+            def __len__(self):
+                return -sys.maxsize-10
+        self.assertRaises(ValueError, len, HugeNegativeLen())
         class NoLenMethod(object): pass
         self.assertRaises(TypeError, len, NoLenMethod())