module ActionMailer::TestCase::Behavior::ClassMethods

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

def mailer_class
  if mailer = self._mailer_class
    mailer
  else
    tests determine_default_mailer(name)
  end
end

def tests(mailer)
  case mailer
  when String, Symbol
    self._mailer_class = mailer.to_s.camelize.constantize
  when Module
    self._mailer_class = mailer
  else
    raise NonInferrableMailerError.new(mailer)
  end
end