Here's the situation: You've got a service that's used by millions of people. You've got a great coverage of unit tests, integration tests, smoke tests and acceptance tests for it. However, in the real world, this service is combined with lots of other services to work correctly, so you need an end-to-end test suite as well to be 99.9% confident that you're safe to deploy a new version. However, if the test is truly end-to-end, it will start sending out fake test data to your millions of user...
