《Crafting Rails 4 Applications》的笔记-第28页

进行邮件测试，你需要在dummy目录下的虚拟程序添加一个配置

In your config/enviroments/test.rb, by default you should have the line config.action_mailer.delivery_method = :test

from

https://stackoverflow.com/questions/3995994/rspec-sends-emails-not-storing-in-actionmailerbase-deliveries-dont-know-wh