This gem checks that migrations do not change the database checksum when they are loaded; via code defined outside of a method. This is to ensure that migrations do not affect the database when they are load, which can lead to some very unexpected database states and often can't be rolled back.
Add this line to your application's Gemfile:
group :test do
gem 'ae_check_migrations_load_silently'
endAnd then execute:
$ bundle
Or install it yourself as:
$ gem install ae_check_migrations_load_silently
To further understand the issues that can be caused by migrations with code that changes the database on load vs on up/down migration, read this TWL! https://sites.google.com/a/appfolio.com/classic-eng/general-engineering-resources/today-we-learned/2020-05-20---migrations-must-not-affect-database-on-load