Added test trying to track down weird segmentation violation from projections with Python 3.13 and MsgStruct instances.

Author: johnbywater

tests/dcb_tests/test_msgpack.py

@@ -0,0 +1,28 @@
+from copy import deepcopy
+from threading import Thread
+from unittest import TestCase
+
+from eventsourcing.dcb.msgpack import Decision
+
+
+class MyDecision(Decision):
+    a: str
+
+
+class Test(TestCase):
+    def test(self) -> None:
+        # Trying to isolate segmentation violation in Python3.13 with
+        # projection using DCB application with ImMemoryDCBRecorder and
+        # eventsourcing.dcb.msgpack.Decision. One suspect is deepcopy of
+        # msgspec.Struct subclasses, perhaps when crossing threads. This
+        # test tries to replicate what InMemoryDCBRecorder does with a
+        # subscription (deepcopy on a different thread). However, no segv.
+        m = MyDecision(a="a")
+        self.assertEqual(deepcopy(m), m)
+
+        def f() -> None:
+            self.assertEqual(deepcopy(m), m)
+
+        t = Thread(target=f)
+        t.start()
+        t.join()