I mean you have felt how Dragon can attack you in the dark and can notice such situations in the future. However some readers may say that this model doesn't reflect the "real" source code. Of course it doesn't. It is too simple. We had considered trivial examples in the simple context.
Let's show the example for "working programmers". Suppose you have the next code block:
X[8] is incorrect. You have no information about presence of other errors. On the clock is alfrfeady 15:55, but your manager demand "the working version" before 11:15 a.m. tomorrow. Seven others "one-line-errors" are waiting for you. I know that rule for 8th element is very simple, but I cannot remember it. Only one I can tell you is that the dozen was important in the previous version. New rule is other, but I had used the existing code to save time. I really wish to help you, but my part should be ready 10:30 a.m. tomorrow and the manager is blaming me too.
Good luck!