A smoke test is a simple test that ensures the basic operation of a system or part of the system. The name comes from the analogy that you are plugging in some electrical equipment and looking to see if smoke comes out.

As a result smoke tests should be very fast to run but not at all comprehensive. An example of a smoke test is a test that opens a database connection and executes a simple query - this just checks that the connection is working. A set of smoke tests are useful to run before a more comprehensive set of tests, since they will quickly fail if there are fundamental faults. It is a good idea to run smoke tests before each step in a deployment pipeline. It is also useful to run smoke tests when deploying into production.