If you want to test App before it is available on the App Store, you could use TestFlight. TestFlight is an App developed by Apple.
Follow these simple 5 steps to become an internal tester:
1.Send Apple ID of your iPhone to App developer. The TestFlight app will use the Apple ID that is currently used for the iTunes Store and the App Store.
2.Install TestFlight From App Store.
3.Check the iTunes Connect invitation email. Tap "activate your account" link in this email and select the "Accept" option.
4.Check the TestFlight invitation email. Tap "View in Testflight" button in this email, the TestFlight App on your iphone will be opened.
5.Tap "INSTALL" button in Testflight, the App you want to test will be installed on your iPhone.
All is done.
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