developing

Test-driven development implements features by writing tests first, then writing minimal code to pass those tests, then refactoring. The RED→GREEN→REFACTOR cycle ensures each change is validated before integration, reducing bugs and improving maintainability across modules.

High cohesion groups related responsibilities within a module; low coupling minimizes dependencies between modules. This architecture pattern improves testability, reduces side effects, and makes features easier to modify without breaking other components.

Organize code with colocation—grouping related logic together—and dependency injection to isolate units for testing. This design enables test-first discipline, simplifies mocking, and enforces clear module boundaries that support the RED→GREEN→REFACTOR cycle.

Yes. TDD applies to bug fixes by writing a failing test that reproduces the issue, then fixing the code to pass it. For architectural refactoring, TDD ensures changes maintain functionality while improving structure, reducing regression risk.

TDD requires understanding design thinking principles, responsibility separation, and your codebase's current architecture. You need a test framework, clear functional and technical requirements, and commitment to strict test-first discipline across planning, implementation, and testing phases.

TDD suits feature delivery, bug resolution, and refactoring when you need high test coverage, quality gates, and confidence in change safety. It's most effective when requirements are clear and you have time to invest in thorough test planning before writing implementation code.