From bdf3513609065fdb16af4b12be29466991923954 Mon Sep 17 00:00:00 2001
From: Joshua King <joshuaking.mba@gmail.com>
Date: Tue, 15 Sep 2026 18:16:40 -0400
Subject: [PATCH] Test fix: build the frozen-snapshot engine on the caller's
 list

Review round 3 (Codex gpt-5.6-terra, LOW): the helper copied the list,
so the mutation could never have affected even a shallow snapshot.
The engine is now constructed directly on the caller's list, making
the freeze regression-proof. Suite green before commit: 997 passed.
---
 tests/test_presence.py | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/tests/test_presence.py b/tests/test_presence.py
index d08b108..ffcb7c7 100644
--- a/tests/test_presence.py
+++ b/tests/test_presence.py
@@ -577,11 +577,18 @@ def test_engine_overlapping_snapshot_uses_latest_start() -> None:
 
 
 def test_engine_override_lists_are_frozen() -> None:
-    """The overrides snapshot must be truly read-only: mutating the
-    caller's list after construction must not change answers."""
+    """The overrides snapshot must be truly read-only: the engine is
+    built directly on the CALLER's list, so mutating that list after
+    construction would change answers under a shallow copy — under the
+    frozen snapshot it must not."""
     entry = PresenceOverride(1, "2026-01-06", "2026-01-06", False)
     entries = [entry]
-    engine = _engine_with_overrides(*entries)
+    schedule = PresenceSchedule(
+        1, 2, ANCHOR, {0: {0, 1, 2, 3, 4, 5, 6}, 1: set()}
+    )
+    engine = PresenceEngine(
+        {1: schedule}, overrides={1: entries}  # caller-owned list
+    )
     assert engine.is_present(1, datetime.date(2026, 1, 6)) is False
     entries.append(PresenceOverride(1, "2026-01-07", "2026-01-07", False))
     # The late append must NOT change the engine's answers...