End-To-End (E2E) testing involves creating automated tests that will test your application as a whole, rather than testing individual chunks of code in isolation (which is the purpose of a unit test).
In this video tutorial, I walk through a real-world application that has some e2e tests implemented and discuss the purpose and value of creating end to end tests in Ionic. The purpose of this video is not to show you how to set up or create e2e tests, but to demonstrate the general concept and explain why it is a worthwhile endeavor.