Clean Code

Test-Driven Development is a discipline - highlights Robert C. Martin. He compares it to the discipline of medical practitioners washing hands between procedures, or the discipline of handling a gun at the shooting range, or the rules at a martial arts dojo. The practice

When code rots, it becomes rigid, fragile, and immobile. Each time you touch it, you risk breaking it in another place. TDD eliminates the fear of change. But can you afford it?

Uncle Bob reminds that source code dependencies should cross the boundaries between the abstract and the concrete pointing from the concrete side towards the abstract side. Concrete -> Abstract As in: Application and Domain Objects ^ | DB Interface Layer | v Database Source: Clean Code

From SOLID principles, your code should be open to extension, and closed to modification. As Uncle Bob points out, classes protect us from new types, while data structures protect us from new functions. This means that when you suspect new functions may be required