tdd

Test-first development is implemented using a structured Red-Green-Refactor loop: write a failing test for public interfaces, implement minimal code to pass it, then refactor the codebase for maintainability and modularity.

Structure tests for observable behavior by targeting public interfaces and designing small, focused modules. This encourages deep modules with hidden implementation details, improving overall testability and refactor-friendly code.

Use mocking effectively during a TDD cycle by applying best practices that isolate external dependencies. Mocking should focus on verifying interactions with public interfaces while maintaining observable behavior without coupling tests to internal code.

Refactor code immediately after the test passes in the Red-Green-Refactor loop. The TDD workflow suggests evaluating common refactoring candidates after each cycle to ensure the codebase maintains high software design quality and modularity.

Yes, test-driven development works for both fixing bugs and implementing new features. It provides a structured workflow that maintains a robust test suite, ensuring code quality and maintainability across all development scenarios.

Test-first development emphasizes deep modules because they provide small, focused interfaces with deep implementation. This separation improves testability, ensures observable behavior is clearly defined, and makes the software design more maintainable.