rails/rails — pull request #14067 by tbloncar (2014-02-15 08:02:24+00:00)
Title: Add documentation/tests around interpolated values in ActiveModel::Errors

Document and test :count option in #add and #added? methods. The purpose of this documentation is to make it clear that the #add and #added? methods should be invoked with the :count option for messages that make use of an interpolated count (by default). Failure to do so will result in an I18n::MissingInterpolationArgument exception.