参考链接：
Test podspec
https://guides.cocoapods.org/using/test-specs.html
OCMock用法
https://www.jianshu.com/p/cad9e7cc6236
如何写一份可测试的代码
https://juejin.im/post/5b87532be51d4538e6333dd0
[iOS单元测试系列]单元测试框架选型
http://zixun.github.io/blog/2015/04/11/iosdan-yuan-ce-shi-xi-lie-dan-yuan-ce-shi-kuang-jia-xuan-xing/