I have nearly spent the whole day increasing the test coverage of one of my project. For traditional employers or ill educated project managers, this could sound like an incredible waste of time. For others, this could sound like pure geeky zealotry or a new mean of self satisfaction for IT nerds.
Indeed, seeing the coverage report display numbers above 80% is extremely satisfying but the true reason for this testing frenzy is elsewhere: this project being bound to play a critical role in the core of the business of my company, testing it thoroughly is simply the only option.
Beyond the assurance such a high coverage buys, the implicit documentation of the system's behavior that an extensive battery of test creates is worth the effort on its own. But there is more. As recently discussed by industry guru Andrew Binstock, writing tests will inevitably lead you to question both design and implementation. Hard to test classes full of not covered "blind spots" will cry for refactoring!
I was amazed to see my code getting simpler and more concise while I was struggling to push the limits of the test coverage. I wish you similar amazing moments!