feat: add persisted batch text testing

backend/services/brains/base.py

@@ -99,6 +99,9 @@ class BrainRuntime:
         Callable[[bool, dict[str, Any]], Awaitable[None]] | None
     ) = None
     flow_global_functions: list[Any] = field(default_factory=list)
+    # Tests replace external side effects without changing Pipecat or stored
+    # tool resources. Production leaves this unset and uses ToolExecutor.
+    tool_executor_factory: Callable[[Any], Any] | None = None
 
 
 @dataclass(frozen=True)