solid

To apply SOLID principles during refactoring, start by writing tests for existing behavior, then incrementally refactor modules toward single responsibility, open-closed, Liskov substitution, interface segregation, and dependency inversion to improve maintainability.

Test-driven development (TDD) is the practice of writing failing tests first, implementing the simplest code to pass them, and refactoring to improve structure, ensuring your clean code remains maintainable and scalable.

Yes, you can use TDD and SOLID principles for architecture planning to enforce design discipline across classes and modules, ensuring the resulting scalable systems remain maintainable throughout development.

The best way to enforce clean code practices during code reviews is to evaluate modules against SOLID principles, verify TDD coverage, and require continuous refactoring to ensure long-term system maintainability.

You should refactor code toward the Single Responsibility Principle (SRP) when a class handles multiple distinct jobs, making it difficult to test or modify, to ensure your software design remains scalable and clean.