I created a Messages Extension in Xcode 8 using the appropriate template, that seems to be working fine and when I run the extension, it's installed in the Messages app and I can use it without any issues.
My problem is that I wanted to create an actual app to be associated with this extension (so that the user would be able to search the extension through the Messages Store or install the actual app through the App Store). I gave it a matching bundle identifier (my extension is com.XXX.testmessage.MessagesExtension, so for the app I set com.XXX.testmessage), but when I run the app, it doesn't install the extension.
Is it possible to do that? And if so, what am I missing?
In XCode8, open your existing app. Then you need to add a new target to your app (File->New->Target->iOS->Sticker Pack Extension (or an iMessage Extension if you want a custom messages experience)). It will then create a folder visible in Project Navigator. The name of the folder depends on the name you gave to the extension. In that folder you will find a Stickers.xcassets where you can drop your stickers.