Unit tests are code too. What ensures the correctness of the tests themselves? My point is simply that you can't simply defer to testing as a cop out to avoid

Unit tests are code too. What ensures the correctness of the tests themselves? My point is simply that you can't simply defer to testing as a cop out to avoid claiming confidence in the correctness of some portion of code. There has to be some amount of code that a dev can pretty well validate simply by inspection. (I'm not saying don't test.)