In-App Messaging allows you to communicate with your users while they are browsing the app, even if they did not accept push notifications. You can easily send a preview to your device before turning the campaign on for all your users.
To achieve that, Batch simulates In-App display by sending you a push notification with your In-App message displayed as a landing page in your app. This will only allow you to see if your text and image are displayed properly.
In the campaign editor, click the ⚙️ to select your device in the saved devices, or copy your advertising id in the corresponding field. Hit "PREVIEW ON MY PHONE".
You will receive a push notification. Open it to see on your device a preview of the message you are editing. If you don't see it right away, you should refer to the Mobile Landing debugging article : My Mobile Landing doesn't show.
Note: Consider turning on the campaign for a development version of your app if you want to test more than the aspect of your message (e.g. trigger, targeting, etc).