1 files changed, 21 insertions, 1 deletions
diff --git a/Lib/json/tests/test_recursion.py b/Lib/json/tests/test_recursion.py
index 548bb89ed5..1f2d7b3b5c 100644
--- a/Lib/json/tests/test_recursion.py
+++ b/Lib/json/tests/test_recursion.py
@@ -16,6 +16,11 @@ class RecursiveJSONEncoder(json.JSONEncoder):
                 return 'JSONTestObject'
         return json.JSONEncoder.default(o)
 
+class EndlessJSONEncoder(json.JSONEncoder):
+    def default(self, o):
+        """If check_circular is False, this will keep adding another list."""
+        return [o]
+
 
 class TestRecursion(TestCase):
     def test_listrecursion(self):
@@ -67,7 +72,7 @@ class TestRecursion(TestCase):
             self.fail("didn't raise ValueError on default recursion")
 
 
-    def test_highly_nested_objects(self):
+    def test_highly_nested_objects_decoding(self):
         # test that loading highly-nested objects doesn't segfault when C
         # accelerations are used. See #12017
         # str
@@ -84,3 +89,18 @@ class TestRecursion(TestCase):
             json.loads(u'{"a":' * 100000 + u'[1]' + u'}' * 100000)
         with self.assertRaises(RuntimeError):
             json.loads(u'[' * 100000 + u'1' + u']' * 100000)
+
+    def test_highly_nested_objects_encoding(self):
+        # See #12051
+        l, d = [], {}
+        for x in xrange(100000):
+            l, d = [l], {'k':d}
+        with self.assertRaises(RuntimeError):
+            json.dumps(l)
+        with self.assertRaises(RuntimeError):
+            json.dumps(d)
+
+    def test_endless_recursion(self):
+        # See #12051
+        with self.assertRaises(RuntimeError):
+            EndlessJSONEncoder(check_circular=False).encode(5j)