Smoke tests

Of course, even when all of your tests succeed, a product can still break in production. The database may be down or maybe you have a website and the web server is down. It is always important to also test whether your software is actually working in a production environment, so be sure to always do an automated smoke test after deployment that gives you fast and detailed feedback when something goes wrong. A smoke test should test whether the most important parts of your system work. A manual smoke test is fine (and I'd always manually check whether your software, at least, runs after a release), but remember it's another human action that may be forgotten or done poorly.

Some people run smoke tests before doing integration and acceptance tests. Integration and acceptance tests test an entire system and, as such, may take a bit of time. A smoke test, however, tests only basic functionality, such as does the page load? When a smoke test fails, you can skip the rest of your tests, saving you some time and giving you faster feedback.