One of the reasons for AngularJS’ success is its outstanding ability to be tested. The main factor that made Sébastien switch from “Well, I just launch the app and see if everything works” to “I’ve got unit tests!” was that, for the first time, he could focus on what matters and on what he enjoys in programming: creating smart algorithms and nice UIs. After having fixed it, re-updated the application and apologized to customer service, he decided to entirely rewrite this component in test-driven development style. The test file ended up being twice as long as the component file. It has been improved a lot since, especially its poor performance, but it never failed again in production. Rock-solid code.