If you can afford to hire a large testing department, this article is not for you.
A Golden Rule of Devops is not to do upgrades when there are insufficient resources for testing. This of course must work in conjunction with the other crucial rule: that of performing critical upgrades timeously.
If you are in charge of a team consisting of programmers and designers you absolutely must make sure that your designers understand these rules. You need to build in the upgrade time for every modification you plan.
Monstrous mistakes are overlooked when there are no interesting changes. Technical upgrades are only interesting to those who live and breathe punin'blers.
If you think your programmers must make no mistakes then you are not paying them enough.
Software improvements—features and bugs—are all quality improvements. Pay attention to the upgrade process and quality will take care of itself.