Launch node when component node is loaded?

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In my logs I have output like this from a component node container:

[INFO] [launch_ros.actions.load_composable_nodes]: Loaded node '/robot_state_publisher' in container '/test_servo_integration_container'

Is there a way in the launch description to trigger launching another node (my gtest) when this happens? Is there a way for me to get the event of load_composable_nodes and launch another node?