Unit Testing: Mandatory or Optional?

I recently came across this nice post (http://agilewarrior.wordpress.com/2012/10/06/its-not-about-the-unit-tests/) and I wanted to share it with you, as it carries a very important message that separates the capable Software Engineers from the great Software Engineers.

In our industry, when we come across a practice that helps us to improve we tend to shout about it and over state its impact. In this post the author points out that Unit Testing is not commonly used in iPhone and iPad development; and yet their software is often highly regarded anyway. As an individual who was taught that high quality software had to be unit tested, this was earth shattering news for him; it literally led to many sleepless nights while he wrestled to incorporate this observation into his view of the world. Needless to say, unit testing is a very powerful tool and that it does belong in every professional software engineers tool box. But knowing when to use it, when not to use it and how to get the best gains from it is important. In fact, like any tool, misusing it can be just as bad as not using it at all. And most of all, unit testing is not a substitute for caring about the product that we are crafting.