feat(phase-32): add automated tests V3 for data sources, scoring, campaigns and snapshots (T-235 to T-237)

backend/app/database.py

@@ -1,12 +1,54 @@
 from sqlalchemy import create_engine
 from sqlalchemy.orm import sessionmaker, declarative_base
 
-from app.config import settings
-
-engine = create_engine(settings.DATABASE_URL)
-SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
 Base = declarative_base()
 
+# Engine and session factory are created lazily so that tests can
+# override DATABASE_URL via environment *before* any import triggers
+# the real PostgreSQL engine creation (which requires psycopg2).
+_engine = None
+_SessionLocal = None
+
+
+def _get_engine():
+    global _engine
+    if _engine is None:
+        from app.config import settings
+        _engine = create_engine(settings.DATABASE_URL)
+    return _engine
+
+
+def _get_session_factory():
+    global _SessionLocal
+    if _SessionLocal is None:
+        _SessionLocal = sessionmaker(
+            autocommit=False, autoflush=False, bind=_get_engine()
+        )
+    return _SessionLocal
+
+
+class _LazySessionLocal:
+    """Proxy so ``SessionLocal()`` keeps working as before but the real
+    sessionmaker is only created on first call."""
+
+    def __call__(self, *args, **kwargs):
+        return _get_session_factory()(*args, **kwargs)
+
+    def __getattr__(self, name):
+        return getattr(_get_session_factory(), name)
+
+
+SessionLocal = _LazySessionLocal()
+
+
+class _EngineProxy:
+    """Thin proxy so ``from app.database import engine`` still works."""
+    def __getattr__(self, name):
+        return getattr(_get_engine(), name)
+
+
+engine = _EngineProxy()  # type: ignore[assignment]
+
 
 def get_db():
     db = SessionLocal()