Debug Builds vs TestFlight for Device Testing
There are a couple of ways to test on a device, here's how to decide which one to use, and make sure you always see the latest app data.
If you only have a few devices you need to test with, make sure you add their UDIDs to your Apple developer account before we generate your certificates. Then you can use a debug build to test:
Debug builds will always have the latest app data, but they do not work to test push notifications or in app purchases. You need to use an Ad Hoc build or TestFlight for that.
TestFlight is the easiest way to test if you have lots of devices to test with, and you can't add them all to your developer account in advance. See this article for how to use TestFlight.
Note that you must press Publish Changes after every new TestFlight build, which updates all apps, not just your test app. If this is not desirable, use debug builds instead.
App not updating?
If your app is not updating, you may need to press Publish Changes on the Build and Preview tab of the app customizer.
Note that this will tell all apps to update, not just your test app.