Summary
- Test-driven development with vertical slices, behavior-focused tests, and incremental red-green-refactor cycles.
- Emphasizes integration-style tests that verify behavior through public APIs, not implementation details; tests should survive refactors unchanged Requires vertical slicing (one test → one implementation → repeat) instead of horizontal slicing (all tests first, then all code), preventing brittle, behavior-insensitive test suites Includes planning phase to confirm interface changes, prioritize behaviors to test, and design for testability before writing code Provides refactoring guidelines covering duplication extraction, module deepening, and SOLID principles, applied only after all tests pass