Without understanding why these rules get broken, it's hard to avoid breaking them. There is a tension between dependency and redundancy. Avoiding redundancy o

Without understanding why these rules get broken, it's hard to avoid breaking them. There is a tension between dependency and redundancy. Avoiding redundancy often introduces dependency as code becomes shared for several purposes. Knowing which is preferable (dependency or redundancy) in a given case requires a lot of judgement and changes as the code evolves. Redundancy is bad when it introduces too much code and too many chances for error or unnecessary divergence of implementation. Dependency is bad when two things that start out closely related diverge in purpose, straining an implementation to handle both cases.