We have a repository with our demo apps for Mongoid and Rails/Sinatra. This repository is mentioned in our documentation.

We do not actually maintain this repo. Apps there use old versions of Mongoid, Rails, and other gems. However, the Mongoid test suite uses these demo apps to make sure they are still "relevant" with newer versions. In order to achieve so, we do some weird adjustments in Gemfiles, apps code. This is far from ideal, and does not really test the demo apps.

We need to agree why we need those demo apps; what versions of Ruby, Rails/Sinatra, and Mongoid they should be run on. Then we bring the apps in accordance with the requirements, and run Mongoid tests only in these setup.