1. promise用法
https://www.cnblogs.com/lvdabao/p/es6-promise-1.html
https://segmentfault.com/a/1190000007032448
2、mocha单元测试参考资料
https://www.jianshu.com/p/9c78548caffa
http://www.ruanyifeng.com/blog/2015/12/a-mocha-tutorial-of-examples.html
https://github.com/mochajs/mocha/wiki
https://mochajs.org/