Upgraded the Rails-based applications from 5.1.7 to 6.0.2.2.

I started by upgrading to the latest version of the Ruby language. I updated .ruby-version and they ran bundle update. And that was all there was to it.

I then tried to create blank 5.1.7 and 6.0.2.1 apps, the way I usually do for Grails apps. But the result didn’t work. There was something conflicted in the knock gem.

For my second attempt, I changed the dependency in Gemfile instead and let Bundler deal with it. I went from ~> 5.1.7 to ~> 5.0 and after running bundle update, it was upgraded to 5.4.2.4. Building on this success, I changed the dependency once more to ~> 6.0, which updated me all the way to version 6.0.2.2. I had to deal with a few deprecations and update RSpec, too, but all the tests are passing and the app is working just fine.