Good tests are almost a pre-requisite to continuous deployment. Usually code is only deployed after passing the tests. Check what "continuous integration" is.

Good tests are almost a pre-requisite to continuous deployment. Usually code is only deployed after passing the tests. Check what "continuous integration" is. You can do continuous deployment without an automated test suite. Heck, I've hacked source code on production servers more times than I like to admit, skipping the deployment part altogether :p Tests are the reason why continuous deployment works. The path going from what the programmer has typed to running on the production server becomes so short, running the test suite non-stop increases confidence on the changes.