fix graph and white background added

python_app/tests/test_shm_ipc.py

@@ -34,6 +34,7 @@ from python_app.orchestration.shm.decoder import (
     decode_result_collection,
     decode_trace_collection,
 )
+from python_app.orchestration.shm.ring_layout import HEADER
 from python_app.orchestration.shm.ring_reader import ShmRingReader
 from python_app.orchestration.shm.ring_writer import ShmRingWriter
 from python_app.storage.npz.serialize import serialize_trace_collection
@@ -304,8 +305,18 @@ class RingOverflowTest(_RingTestCase):
                 writer.push(b"new")
 
         with mock.patch.object(atomics, "fence", side_effect=overwrite_after_copy):
-            self.assertIsNone(reader.pop_payload())
-        self.assertEqual(reader.pop_payload(), b"new")
+            self.assertEqual(reader.pop_payload(), b"new")  # the torn copy is never returned
+        self.assertIsNone(reader.pop_payload())
+
+    def test_lapped_reader_continues_with_the_newest_payload(self) -> None:
+        name = self._ring_name()
+        writer = self._writer(name, capacity=4, slot_size=64)
+        reader = self._reader(name)
+        for i in range(3):
+            writer.push(f"f{i}".encode())
+        writer._write_u64(HEADER.size + 8, 0)  # the producer is overwriting the unread f0
+        self.assertEqual(reader.pop_payload(), b"f2")
+        self.assertIsNone(reader.pop_payload())
 
     def test_reader_cannot_rewind_cursor_after_producer_laps_during_commit(self) -> None:
         from python_app.orchestration.shm import atomics