solid-principles

SOLID principles guide separating concerns, defining clear responsibilities, and structuring dependencies to reduce coupling and improve maintainability. Start by identifying single responsibilities in your modules, then refactor to split concerns and add focused tests.

Single responsibility means each module handles one reason to change. Interface segregation means clients depend only on methods they use, not bloated interfaces. Together they eliminate unnecessary coupling and make refactoring safer.

Yes. SOLID applies across languages through language-appropriate patterns: TypeScript uses interfaces and class hierarchies; Elixir uses behaviours and protocol-based composition. Both satisfy the five principles with idiomatic implementations.

The open/closed principle means modules should be open for extension but closed for modification. If adding new features requires changing existing code rather than adding new implementations, your design is too tightly coupled to specifics.

Liskov substitution ensures subtypes can replace their parent types without breaking behavior. Violating it causes unexpected errors when code relies on inherited contracts. Enforce it by ensuring derived types honor parent contracts exactly.

Refactor when adding features requires modifying existing modules, tests become fragile, or responsibilities blur across functions. SOLID prevents these pain points; apply it during implementation and when refactoring reaches natural boundaries.