RSpec::Matchers.define :ensure_valid_isin_format_of do |attribute| match do |model| model.send("#{attribute}=", "1234") model.valid? if model.errors.has_key?(attribute) model.errors[attribute].include?(I18n.t("active_validation.errors.messages.isin")) end end failure_message do |model| I18n.t( "active_validation.errors.matchers.ensure_valid_isin_format_of.failure_message_for_should", attr: attribute.inspect, model: model.class.name ) end failure_message_when_negated do |model| I18n.t( "active_validation.errors.matchers.ensure_valid_isin_format_of.failure_message_for_should_not", attr: attribute.inspect, model: model.class.name ) end end