Sometimes you will be caught between a rock and a hard place. For example: You really need to upgrade your Rails application because Heroku is discontinuing your stack in two weeks so you don't have the time to write an entire test suite.
Sometimes the situation will be that your boss really needs you to upgrade Ruby or Rails to use a version that gets security updates and they won't allow you to write tests beforehand.
This article will explain how to ship a Rails upgrade project without a test suite. If your application has no tests, you will learn how to upgrade without having to write tests first.Read more