If you want to use PubSub the you can find example data in the PubSub docs which you can use to mock custom channel points rewards.
I’d suggest that you move away from using PubSub and instead use EventSub which provides a great deal more information for channel points rewards that your app uses. The EventSub docs also provide example notification data which you can use to mock incoming notifications, as well as the Twitch CLI has the capability to mock notifications.