End-to-End testing tests your entire system from one end to the other. Doing it this way makes everything from one end to the other black box. Using this way of testing, it will catch bugs across you entire system. The downside to End-to-End testing is it can be slower, less reliable and harder to maintain. Using this kind of testing you’ll want to focus more on the overall system health rather than focusing on small details.
Doing testing this way is not right for every situation. It is expensive to maintain and can be slow. The advantages may out weight the disadvantages in certain situations.
https://testing.googleblog.com/2016/09/testing-on-toilet-what-makes-good-end.html
Software Testing 