When your product grows you normally shouldn't have time to evaluate all the cases. That's why you write unit-tests - so you wouldn't need to review all the cas

When your product grows you normally shouldn't have time to evaluate all the cases. That's why you write unit-tests - so you wouldn't need to review all the cases when introducing new functionality. E.g. one of the product I was working on recently is made from several components. Couple components have 100+ unit-tests.