module ThoughtBot::Shoulda::ActionMailer::Assertions

def assert_did_not_send_email
  msg = "Sent #{::ActionMailer::Base.deliveries.size} emails.\n"
  ::ActionMailer::Base.deliveries.each { |m| msg << "  '#{m.subject}' sent to #{m.to.to_sentence}\n" }
  assert ::ActionMailer::Base.deliveries.empty?, msg
end