refactor(tests): centralize fake database import-state cleanup

Test-only refactor continuing #2523. Centralizes the repeated guarded fake core.database/src.database import-state cleanup into a focused helper.

tests/helpers/import_state.py

@@ -8,6 +8,10 @@ had before the block — present, absent, or carrying a parent-package attribute
 Use ``clear_module`` to drop a single module from both ``sys.modules`` and its
 parent-package attribute (e.g. before forcing a fresh import inside the block).
 
+Use ``clear_fake_database_modules`` to evict a *stubbed* ``core.database`` (and
+its companion ``src.database``) that another test left in import state, without
+touching a real ``core.database`` loaded from disk.
+
 Background: importing ``routes.session_routes`` also sets ``session_routes`` on
 the parent ``routes`` package object. A ``from routes import session_routes``
 or ``import routes.session_routes as X`` statement resolves through that parent
@@ -60,6 +64,35 @@ def clear_module(dotted_name):
     _restore_one(dotted_name, _ABSENT, _ABSENT)
 
 
+def clear_fake_database_modules():
+    """Evict a *stubbed* ``core.database`` (and ``src.database``) from import state.
+
+    Test-only. Some tests install a fake ``core.database`` — a stub module with
+    no on-disk ``__file__`` — into ``sys.modules`` and onto the ``core`` package.
+    A later test that needs the real database module must evict that stub first,
+    or its ``import core.database`` resolves to the fake.
+
+    This is deliberately conservative and mirrors the per-file helpers it
+    replaces:
+
+    * It acts only when ``core.database`` is a fake/stub, detected by a missing
+      string ``__file__``. A real ``core.database`` loaded from disk is left
+      untouched, as is the case where nothing is cached.
+    * When it does act, it also drops the cached ``src.database`` entry.
+    * It removes the ``core.database`` parent-package attribute only when that
+      attribute is the same fake object being evicted.
+    """
+    parent = sys.modules.get("core")
+    attr = getattr(parent, "database", None) if parent is not None else None
+    mod = sys.modules.get("core.database") or attr
+    if mod is None or isinstance(getattr(mod, "__file__", None), str):
+        return
+    sys.modules.pop("core.database", None)
+    sys.modules.pop("src.database", None)
+    if parent is not None and attr is mod:
+        delattr(parent, "database")
+
+
 @contextmanager
 def preserve_import_state(*module_names):
     """Save and restore sys.modules entries and parent-package attributes.

tests/test_calendar_rrule.py

@@ -15,20 +15,9 @@ from sqlalchemy import create_engine
 from sqlalchemy.orm import sessionmaker
 from sqlalchemy.pool import NullPool
 
+from tests.helpers.import_state import clear_fake_database_modules
 
-def _drop_fake_core_database():
+clear_fake_database_modules()
-    parent = sys.modules.get("core")
-    attr = getattr(parent, "database", None) if parent is not None else None
-    mod = sys.modules.get("core.database") or attr
-    if mod is None or isinstance(getattr(mod, "__file__", None), str):
-        return
-    sys.modules.pop("core.database", None)
-    sys.modules.pop("src.database", None)
-    if parent is not None and attr is mod:
-        delattr(parent, "database")
-
-
-_drop_fake_core_database()
 
 import core.database as cdb
 from core.database import CalendarEvent

tests/test_document_close_clears_active_route.py

@@ -13,7 +13,6 @@ while completing reliably everywhere.
 """
 
 import tempfile
-import sys
 import uuid
 from types import SimpleNamespace
 
@@ -22,20 +21,9 @@ from sqlalchemy.orm import sessionmaker
 from sqlalchemy.pool import NullPool
 from unittest.mock import MagicMock
 
+from tests.helpers.import_state import clear_fake_database_modules
 
-def _drop_fake_core_database():
+clear_fake_database_modules()
-    parent = sys.modules.get("core")
-    attr = getattr(parent, "database", None) if parent is not None else None
-    mod = sys.modules.get("core.database") or attr
-    if mod is None or isinstance(getattr(mod, "__file__", None), str):
-        return
-    sys.modules.pop("core.database", None)
-    sys.modules.pop("src.database", None)
-    if parent is not None and attr is mod:
-        delattr(parent, "database")
-
-
-_drop_fake_core_database()
 
 import core.database as cdb
 import routes.document_routes as droutes

tests/test_helpers_import_state.py

@@ -4,10 +4,18 @@ import types
 
 import pytest
 
-from tests.helpers.import_state import clear_module, preserve_import_state
+from tests.helpers.import_state import (
+    clear_fake_database_modules,
+    clear_module,
+    preserve_import_state,
+)
 
 _SENTINEL = "tests._import_state_test_sentinel"
 
+# Names touched by clear_fake_database_modules — snapshot/restore these so the
+# tests never leak into the real core/src packages.
+_DB_NAMES = ("core", "core.database", "src", "src.database")
+
 
 def test_absent_module_is_removed_after_block():
     assert _SENTINEL not in sys.modules
@@ -139,3 +147,106 @@ def test_parent_attr_restored_correctly_when_parent_also_preserved():
     finally:
         sys.modules.pop("_fake_istate_parent", None)
         sys.modules.pop("_fake_istate_parent.child", None)
+
+
+def test_clear_fake_database_removes_stub_core_database():
+    with preserve_import_state(*_DB_NAMES):
+        fake_core = types.ModuleType("core")
+        fake_db = types.ModuleType("core.database")  # no __file__ => a stub
+        fake_core.database = fake_db
+        sys.modules["core"] = fake_core
+        sys.modules["core.database"] = fake_db
+
+        clear_fake_database_modules()
+
+        assert "core.database" not in sys.modules
+        assert not hasattr(fake_core, "database")
+
+
+def test_clear_fake_database_preserves_real_core_database():
+    with preserve_import_state(*_DB_NAMES):
+        fake_core = types.ModuleType("core")
+        real_db = types.ModuleType("core.database")
+        real_db.__file__ = "/somewhere/core/database.py"  # looks on-disk
+        fake_core.database = real_db
+        sys.modules["core"] = fake_core
+        sys.modules["core.database"] = real_db
+
+        clear_fake_database_modules()
+
+        assert sys.modules["core.database"] is real_db
+        assert fake_core.database is real_db
+
+
+def test_clear_fake_database_drops_src_database_when_core_is_fake():
+    with preserve_import_state(*_DB_NAMES):
+        fake_core = types.ModuleType("core")
+        fake_db = types.ModuleType("core.database")
+        fake_core.database = fake_db
+        sys.modules["core"] = fake_core
+        sys.modules["core.database"] = fake_db
+        sys.modules["src.database"] = types.ModuleType("src.database")
+
+        clear_fake_database_modules()
+
+        assert "src.database" not in sys.modules
+
+
+def test_clear_fake_database_leaves_src_database_when_core_is_real():
+    with preserve_import_state(*_DB_NAMES):
+        fake_core = types.ModuleType("core")
+        real_db = types.ModuleType("core.database")
+        real_db.__file__ = "/somewhere/core/database.py"
+        fake_core.database = real_db
+        sys.modules["core"] = fake_core
+        sys.modules["core.database"] = real_db
+        src_db = types.ModuleType("src.database")
+        sys.modules["src.database"] = src_db
+
+        clear_fake_database_modules()
+
+        assert sys.modules["src.database"] is src_db
+
+
+def test_clear_fake_database_keeps_parent_attr_pointing_elsewhere():
+    """When the cached core.database is a stub but the `database` attr on the
+    core package points at a *different* object, the attr is left intact —
+    only the same fake object is unlinked."""
+    with preserve_import_state(*_DB_NAMES):
+        fake_core = types.ModuleType("core")
+        cached_fake = types.ModuleType("core.database")  # the stub in sys.modules
+        other = types.ModuleType("core.database")  # parent attr points here
+        fake_core.database = other
+        sys.modules["core"] = fake_core
+        sys.modules["core.database"] = cached_fake
+
+        clear_fake_database_modules()
+
+        assert "core.database" not in sys.modules
+        assert fake_core.database is other
+
+
+def test_clear_fake_database_uses_parent_attr_when_not_in_sys_modules():
+    """A stub reachable only via the core package's `database` attribute (not in
+    sys.modules) is still detected and unlinked from the parent."""
+    with preserve_import_state(*_DB_NAMES):
+        sys.modules.pop("core.database", None)
+        fake_core = types.ModuleType("core")
+        fake_db = types.ModuleType("core.database")
+        fake_core.database = fake_db
+        sys.modules["core"] = fake_core
+
+        clear_fake_database_modules()
+
+        assert not hasattr(fake_core, "database")
+
+
+def test_clear_fake_database_noop_when_nothing_cached():
+    with preserve_import_state(*_DB_NAMES):
+        sys.modules.pop("core.database", None)
+        fake_core = types.ModuleType("core")  # no `database` attr
+        sys.modules["core"] = fake_core
+
+        clear_fake_database_modules()  # must not raise
+
+        assert "core.database" not in sys.modules

tests/test_sqlite_foreign_keys.py

@@ -1,22 +1,10 @@
 import pytest
-import sys
 from sqlalchemy import create_engine
 from sqlalchemy.orm import sessionmaker
 
+from tests.helpers.import_state import clear_fake_database_modules
 
-def _drop_fake_core_database():
+clear_fake_database_modules()
-    parent = sys.modules.get("core")
-    attr = getattr(parent, "database", None) if parent is not None else None
-    mod = sys.modules.get("core.database") or attr
-    if mod is None or isinstance(getattr(mod, "__file__", None), str):
-        return
-    sys.modules.pop("core.database", None)
-    sys.modules.pop("src.database", None)
-    if parent is not None and attr is mod:
-        delattr(parent, "database")
-
-
-_drop_fake_core_database()
 
 from core.database import Base, Session, ChatMessage
 from datetime import datetime

tests/test_task_scheduler_session_delivery.py

@@ -12,20 +12,9 @@ if not isinstance(sqlalchemy, _types.ModuleType):
 from sqlalchemy import create_engine
 from sqlalchemy.orm import sessionmaker
 
+from tests.helpers.import_state import clear_fake_database_modules
 
-def _drop_fake_core_database():
+clear_fake_database_modules()
-    parent = sys.modules.get("core")
-    attr = getattr(parent, "database", None) if parent is not None else None
-    mod = sys.modules.get("core.database") or attr
-    if mod is None or isinstance(getattr(mod, "__file__", None), str):
-        return
-    sys.modules.pop("core.database", None)
-    sys.modules.pop("src.database", None)
-    if parent is not None and attr is mod:
-        delattr(parent, "database")
-
-
-_drop_fake_core_database()
 
 import core.database as cdb
 from core.database import Base, Session as DbSession

tests/test_topic_analyzer.py

@@ -1,24 +1,12 @@
 """Tests for topic keyword matching (src/topic_analyzer.py)."""
-import sys
 from types import SimpleNamespace
 import pytest
 from sqlalchemy import create_engine
 from sqlalchemy.orm import sessionmaker
 
+from tests.helpers.import_state import clear_fake_database_modules
 
-def _drop_fake_core_database():
+clear_fake_database_modules()
-    parent = sys.modules.get("core")
-    attr = getattr(parent, "database", None) if parent is not None else None
-    mod = sys.modules.get("core.database") or attr
-    if mod is None or isinstance(getattr(mod, "__file__", None), str):
-        return
-    sys.modules.pop("core.database", None)
-    sys.modules.pop("src.database", None)
-    if parent is not None and attr is mod:
-        delattr(parent, "database")
-
-
-_drop_fake_core_database()
 
 from core.database import Base, Session as DbSession, ChatMessage as DbChatMessage
 from core.session_manager import SessionManager