Update test_gc from v3.14.3

RustPython · youknowone · Mar 12, 2026 · Mar 5, 2026 · Mar 5, 2026 · Mar 5, 2026
commit c889a96bdc3f25ce9f025f7573f53ca44dc63a04
diff --git a/Lib/test/_test_gc_fast_cycles.py b/Lib/test/_test_gc_fast_cycles.py
@@ -0,0 +1,48 @@
+# Run by test_gc.
+from test import support
+import _testinternalcapi
+import gc
+import unittest
+
+class IncrementalGCTests(unittest.TestCase):
+
+    # Use small increments to emulate longer running process in a shorter time
+    @support.gc_threshold(200, 10)
+    def test_incremental_gc_handles_fast_cycle_creation(self):
+
+        class LinkedList:
+
+            #Use slots to reduce number of implicit objects
+            __slots__ = "next", "prev", "surprise"
+
+            def __init__(self, next=None, prev=None):
+                self.next = next
+                if next is not None:
+                    next.prev = self
+                self.prev = prev
+                if prev is not None:
+                    prev.next = self
+
+        def make_ll(depth):
+            head = LinkedList()
+            for i in range(depth):
+                head = LinkedList(head, head.prev)
+            return head
+
+        head = make_ll(1000)
+
+        assert(gc.isenabled())
+        olds = []
+        initial_heap_size = _testinternalcapi.get_tracked_heap_size()
+        for i in range(20_000):
+            newhead = make_ll(20)
+            newhead.surprise = head
+            olds.append(newhead)
+            if len(olds) == 20:
+                new_objects = _testinternalcapi.get_tracked_heap_size() - initial_heap_size
+                self.assertLess(new_objects, 27_000, f"Heap growing. Reached limit after {i} iterations")
+                del olds[:]
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/Lib/test/test_gc.py b/Lib/test/test_gc.py
@@ -822,7 +822,7 @@ def test_get_stats(self):
         for st in stats:
             self.assertIsInstance(st, dict)
             self.assertEqual(set(st),
-                             {"collected", "collections", "uncollectable", "candidates", "duration"})
+                             {"collected", "collections", "uncollectable"})
             self.assertGreaterEqual(st["collected"], 0)
             self.assertGreaterEqual(st["collections"], 0)
             self.assertGreaterEqual(st["uncollectable"], 0)