test(backend): stop test_action_items_timezone from poisoning sys.modules (#8661)

[ZachL111]

What

Fixes the test_action_items_timezone.py part of #8661.

This file installed its stubs by writing to sys.modules at module scope and never restored them. The _stub_package() helper replaced real packages (utils, utils.retrieval, utils.retrieval.tools, utils.conversations, database, langchain_core) with empty types.ModuleType stubs. During a bulk pytest tests/unit/ run, pytest collects every file, so this file's module-level code ran and permanently replaced those packages, and every test file collected alphabetically after it then failed to import from them.

Fix

Snapshot sys.modules before the stubbing begins, and restore it right after the module under test (action_item_tools) is imported:

_SYS_MODULES_SNAPSHOT = dict(sys.modules)
# ... install stubs, load the module under test ...
for _name in list(sys.modules):
    if _name in _SYS_MODULES_SNAPSHOT:
        if sys.modules[_name] is not _SYS_MODULES_SNAPSHOT[_name]:
            sys.modules[_name] = _SYS_MODULES_SNAPSHOT[_name]
    else:
        del sys.modules[_name]

The loaded module keeps its references to the stubbed dependencies (Python binds them at import time), and the tests patch action_item_tools.action_items_db directly rather than by string path, so the restore does not change behaviour.

Verification

pytest tests/unit/test_action_items_timezone.py -q                 # 11 passed (own tests unchanged)
pytest tests/unit/test_action_items_timezone.py \
       tests/unit/test_apps_create_app_json.py -q                  # 26 passed (was a collection ERROR before)

This addresses one of the three module-level-stub files in #8661. The other two (test_action_item_date_validation.py, test_tools_router.py) and the missing fake-firestore dependency are out of scope here.

[cubic-dev-ai]

No issues found across 1 file

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

_{Re-trigger cubic}

[Git-on-my-level]

Thanks for isolating this — the fix is small and targeted, and the approach makes sense for the current test structure.

I reviewed the diff and ran the focused regression locally in a clean worktree with secrets stripped:

python -m pytest tests/unit/test_action_items_timezone.py tests/unit/test_apps_create_app_json.py -q

Result: 26 passed.

I’m leaving this as a positive signal rather than a formal approval because this is explicitly one slice of the broader #8661 sys.modules/test-isolation cleanup, so a human maintainer should decide whether to merge this partial fix as-is or wait for the remaining related cleanup. No blocking code concerns from my review.

[kodjima33]

test-only stabilization: stop test_action_items_timezone poisoning sys.modules (#8661); CI green