Nowaday, all the code should be tested before shipped. But we are all human being, we make mistakes. Sometime you are thinking just one line of code, not a big deal, just push it. Unfortunately, that line of code cause errors. So, we need something to automate test our codes after we pushed it to verify our code pass all the test case or not. That’s why CI introduced.

And for CI, in my option, there are two kinds right now, one is Jenkins with docker(more manual) and one is Codeship/travis-ci(more automated).