tdd-feature-development_skill

Overview

This skill enforces test-driven development practices before any feature development begins. It ensures tests are planned explicitly, written early alongside implementation, and that designs remain testable to achieve reliable, maintainable code.

How this skill works

When a user requests a feature, invoke this skill first to establish TDD requirements and a testing-first plan. It produces TODO-style steps that separate test-writing from implementation, enforces behavior-focused tests, and sets a target coverage baseline to guide the subsequent feature-dev workflow.

When to use it

• When the user asks to implement, add, or build any new feature
• Before invoking any feature development workflow (e.g., feature-dev)
• When creating implementation plans, TODO lists, or user stories
• During discovery, architecture design, and implementation planning
• When assessing testability of proposed designs

Best practices

• Make every test-writing activity an explicit TODO item separate from implementation
• Write tests early — alongside or immediately before implementing each piece of functionality
• Test observable behavior and public APIs; avoid testing private/internal functions
• Design code for testability: inject dependencies and isolate core logic for unit tests
• Aim for at least 80% test coverage as a baseline and include a final coverage check in the plan

Example use cases

• User requests a new authentication endpoint — produce a plan that lists tests for success, validation, and failure cases before implementation
• Planning a new microservice — add TODOs for interface design, behavior tests, mockable dependency wiring, then implementation
• Adding a feature flag — write tests for toggle behavior and rollout scenarios before coding the flag logic
• Refactoring a module — create tests for the public behavior first, then refactor safely with tests guarding regressions