Since Rails 5.1 there are additional methods to use in callback to track attribute changes, including 'saved_change_to_attribute' and 'attribute_before_last_save'. See this PR for details.

Since Mongoid strives to maintain compatibility with ActiveRecord whenever possible, these method should be implemented.

Original description
attribute_changed? and attribute_was ActiveRecord methods will be deprecated inside of after_(create|update|save) callbacks source

Does Mongoid support mettods saved_change_to_attribute? and attribute_before_last_save to maintain consistency ?

Additionally support will_save_change_to_attribute.