This is good in theory, and often in practice, but not always. If this practice is followed blindly, unit tests can become too tightly bound to the code to the

This is good in theory, and often in practice, but not always. If this practice is followed blindly, unit tests can become too tightly bound to the code to the point where every code change is assumed to require corresponding 1:1 unit test changes and it becomes difficult to distinguish between a broken test that signals broken functionality versus one that simply hasn't been 'synced' yet.