https://github.com/google/googletest/tree/master/googlemock
https://blog.csdn.net/hhb200766/article/details/81389947
https://github.com/powermock/powermock
https://www.jianshu.com/p/0f17bd2410e4
https://github.com/mockito/mockito/wiki/How-to-write-good-tests