Validate that __length_hint__ returns a usable result.

1 files changed, 10 insertions, 0 deletions

diff --git a/Lib/test/test_iterlen.py b/Lib/test/test_iterlen.py
index 91873c2af4..ab5466ecf9 100644
--- a/Lib/test/test_iterlen.py
+++ b/Lib/test/test_iterlen.py
@@ -208,6 +208,11 @@ class BadLengthHint(object):
     def __length_hint__(self):
         raise RuntimeError('hello')
 
+class NoneLengthHint(object):
+    def __iter__(self): return iter(range(10))
+    def __length_hint__(self):
+        return None
+
 class TestLengthHintExceptions(unittest.TestCase):
 
     def test_issue1242657(self):
@@ -225,6 +230,11 @@ class TestLengthHintExceptions(unittest.TestCase):
         self.assertRaises(RuntimeError, b.extend, BadLen())
         self.assertRaises(RuntimeError, b.extend, BadLengthHint())
 
+    def test_invalid_hint(self):
+        # Make sure an invalid result doesn't muck-up the works
+        self.assertEqual(list(NoneLengthHint()), list(range(10)))
+
+
 def test_main():
     unittests = [
         TestRepeat,