End-to-end (e2e) testing is the practice of testing an application from start to finish to determine whether all the components are working together properly. If unit tests are the first line of defense against bugs within the individual components, e2e testing can be thought of as the safety net that catches issues related to integration and flow within an application. The AngularJS team built Protractor, a Node.js application that can simulate user interactions and help developers test the overall health of their AngularJS applications. It’s a good idea to ask an applicant about past experiences using Protractor to perform e2e testing on AngularJS applications.