We are going to use some of our test code in production. Yes you read it right test code in production. Here are the details
In our system, among other things, we support visual search in video calls. i.e. an end user calls the system, points the camera at something she is interested, and (hopefully :) ) gets relevant information. Basically the system is made of several resources (image extraction, identification etc.) that collaborate via an event broker. We have a blogjecting watchdog that makes sure everything is up and running and we have applicative recovery service to handle failures.
The watchdog makes sure resources/services are up, resources report their liveliness and wellness so we know more about the resources than the fact that they are up. However, we still need a way to make sure that resource instances  can collaborate to provide the service.

Enter our automated acceptance tests. Part of our development effort included building a test runner for automated tests scenarios, e.g. load tests, verifying algorithms correctness etc. One of these tests is the smoke test (run after each successful build) which includes a sunny-day scenario of a video call- as described above. What we're going to do now is build on the test runner and the sunny day scenario a "keep-alive" tester that will periodically make test calls to the system (depending on the current load etc.) and make sure that everything is still working correctly.


So there you have it, an unexpected benefit of automated acceptance tests, who would have thunk it :)