Improve code coverage to 100%

[jurieotto]

It would be nice to get the code coverage to 100%. Then the report would immediately jump out at you whenever a line of code is missed during any newly added feature.

I would not mind getting stuck in the testing, but most of the unit testing python packages and tools are new to me. @bryanyang0528 would it perhaps be possible for you to add some unit testing instructions to help me getting started with this endeavor?

[bryanyang0528]

@jurieotto The unit test of this project is complicated because I use vcrpy(https://github.com/kevin1024/vcrpy) to simulate responses from KSQL server. You can read more information about vcrpy here(https://github.com/kevin1024/vcrpy).

I'm not sure if it's the best way for unit testing, but it's rather easy than use mock for API. If you have any suggestions, please don't be hesitate and let me know. Maybe I can add an instruction first and we can disscuss it. Thank you.

[KenCox94]

will get on this as soon as I can