Ruby gives you a great power, such as easy Duck Typing. As the saying goes, "With great power there must also comes great responsibility!" It comes at a price. We cannot afford to blow off everything when shipping. That's why it's important to put in place different strategies to help us to catch errors asap, but also to avoid the cruft long term. Like a safety net, they allow you to go forward with more confidence.
presented at RedDotRubyConference 2014 http://www.reddotrubyconf.com/
Code available at https://github.com/8thcolor/rdrc2014-safetynets
Video available at http://www.confreaks.com/videos/4106-rdrc2014-safety-nets-learn-to-code-with-confidence