How do you know your feature is working perfectly in production? And if something breaks in production, how will you know? Will you wait for a user to report it to you? What do you do when your staging test results do not reflect current production behavior? In order to test proactively as opposed to reactively, test in production! You will have increased accuracy of test results, your tests will run faster due to elimination of mock and bad data, and you will have higher confidence before releases. You can accomplish this through feature flagging, continuous delivery, and data cleanup. Only when your end-to-end tests pass in production will you know that your features are truly working.