Failed smog

Absolutely. Most cars have a number of self-tests the Engine Computer runs, but only under certain conditions. If those tests pass, that is enough in some states. No other manual testing is required. Typically you need to do some combination of things like a brief burst of wide-open-throttle, a specific amount of highway speed driving without letting off the accelerator, and things like that. Many mechanics know what is required during a "drive cycle" for a few car models, but the idea is you should be able to meet the requirements during normal driving. Sometimes the tests pass in a day or two. Sometimes it can take a week or more before every test is run and passed.