The as_deprecation_tracker gem is designed to monitor ActiveSupport deprecation calls during tests and prevent new code triggering deprecation warnings by maintaining a whitelist. This will be important when upgrading Rails so regressions aren't introduced.

The whitelist is similar to the idea of a RuboCop TODO file where deprecation warnings that are known to be triggered by the application can be listed, keyed by the deprecation warning message. This can also be restricted to certain files, so known deprecations can be permitted in existing code while not permitting the deprecation to be added in another file. New deprecation warnings then raise exceptions in tests.

Some leeway needs to be given to plugins to allow their code to call deprecated code in both Rails and Foreman unless they specify their own whitelist.