determine_default_mailer

# File actionmailer/lib/action_mailer/test_case.rb, line 49
        def determine_default_mailer(name)
          mailer = determine_constant_from_test_name(name) do |constant|
            Class === constant && constant < ActionMailer::Base
          end
          raise NonInferrableMailerError.new(name) if mailer.nil?
          mailer
        end