So you've completed that latest feature but what did you, potentially, forget to test? This presentation tries to demonstrate some of the those things you might have forgot to test and what you might be able to do to combat them.
A question on Stack Overflow that shows both the complexity and variety of answers, coupled with some decent links to some great blog posts on the topic.
A great article on staged rollouts for Android via the Google Play Store
Useful for migration testing as described in the slides amongst other things.
Full depth guide on launch modes, stacks and much more from Google.