I have five people testing my app. It was signed with a debug key.
Now, i want to release it, so i signed it with my keystore. Android can't just upgrade the installation because of that (I tought i could do that), so i have to uninstall the debug apk to install the release version. Is there any way to keep the database from the debug apk to use on the release apk?
You could do this in very manual fashion by updating the debug version to save the database to a public location, then adding a function in your release apk to read from that file. Probably you should then update your release apk again to remove that function once all of your users have transferred to the release version.
I suspect there isn't a much better way to do this, because of how Android sandboxes apps signed with different keys from each other.