This is an excellent and simple anecdote of someone discovering why TDD (and its siblings) is a fundamental core skill in software development.<p>What I really like here is that the author has provided a simple numerical explanation for the cause of his problem. Very useful.
Testing is not related to small or big code base.<p>A good programmer can code with automatic testing in his head, so in his view it doesn't need testing. But this is a personal supposition.