def start(self) -> AppHarness:
        """Start the backend in a new thread and dev frontend as a separate process.

        Returns:
            self
        """
        self._initialize_app()
        self._start_backend()
        self._start_frontend()
        self._wait_frontend()
        return self
Start the backend in a new thread and dev frontend as a separate process.

        Returns:
            self
        
reflex/testing.py