refactor(tests): add temp sqlite helper (#2930)

tests/helpers/sqlite_db.py

@@ -0,0 +1,29 @@
+"""Construct a file-backed temp sqlite DB for tests.
+
+Only builds the SQLAlchemy objects from the repeated temp-sqlite block. It
+does not patch modules, manage cleanup, or own any global state — the caller
+keeps the returned objects alive and binds ``SessionLocal`` where needed.
+"""
+import tempfile
+
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+from sqlalchemy.pool import NullPool
+
+
+def make_temp_sqlite(metadata):
+    """Build a file-backed temp sqlite database and create its tables.
+
+    Returns ``(SessionLocal, engine, tmpfile)``. The caller must keep these
+    references alive (temp file and engine GC are the caller's concern) and
+    bind ``SessionLocal`` onto whatever module the code under test reads.
+    """
+    tmpfile = tempfile.NamedTemporaryFile(suffix=".db", delete=False)
+    engine = create_engine(
+        f"sqlite:///{tmpfile.name}",
+        connect_args={"check_same_thread": False},
+        poolclass=NullPool,
+    )
+    metadata.create_all(engine)
+    SessionLocal = sessionmaker(bind=engine, autoflush=False, autocommit=False)
+    return SessionLocal, engine, tmpfile