Testing isn't just about preventing bugs, it also encourages better design, and good design makes extending and enhancing your application much easier and faster.
...in general, of course, there's always exceptions, don't be dogmatic.
...in general, of course, there's always exceptions, don't be dogmatic.
In short, it's better to think of unit testing as bug-prevention mechanism. Thinking of it as an ultimate design mechanism doesn't end up well.