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test-driven-development

Guides test-first development using the red-green-refactor cycle for code changes and bug fixes.

Updated Jun 23, 2026
Search Tags:#code quality#unit tests#testing#tdd#bug fixing#red green refactor#test pyramid
One-click install
npx skills add https://github.com/jampissarandev/Expense-Tracker --skill test-driven-development-jampissarandev
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: test-driven-development
Source: https://github.com/jampissarandev/Expense-Tracker/tree/main/.github/skills/test-driven-development
Command: npx skills add https://github.com/jampissarandev/Expense-Tracker --skill test-driven-development-jampissarandev

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes references (resource) components.

What problem does it solve? Code changes made without tests ship unverified behavior, and bug fixes without reproduction tests leave regressions undetected. This Skill enforces a disciplined workflow where every behavior change is proven by a failing-then-passing test. ## Core Features & Use Cases - Red-Green-Refactor Cycle: Write a failing test first, implement minimal code to pass it, then refactor with tests as a safety net. - Prove-It Pattern for Bugs: Reproduce any reported bug with a failing test before attempting a fix, guaranteeing the fix actually works. - Test Quality Guidance: Covers the test pyramid, DAMP vs DRY in tests, state-based assertions over mocks, and anti-patterns to avoid. - Use Case: A bug report says completing a task doesn't set its timestamp. Write a failing test that asserts completedAt is set, confirm it fails, implement the fix, and watch it pass — the regression is now permanently guarded. ## Quick Start Ask the agent to implement a new feature or fix a bug using test-driven development, starting with a failing test before any implementation code.

Frequently Asked Questions about test-driven-development

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I practice test-driven development when fixing a bug?▼

Write a test that reproduces the bug first and confirm it fails, proving the bug exists. Then implement the fix and verify the test passes, followed by running the full suite to catch regressions.

What is the red-green-refactor cycle in TDD?▼

Red means writing a failing test for the desired behavior, green means writing the minimal code to make it pass, and refactor means cleaning up the implementation while keeping tests green. The cycle repeats for each new behavior.

Should I use mocks or real implementations in unit tests?▼

Prefer real implementations first, then fakes, stubs, and finally mocks as a last resort. Reserve mocks for dependencies that are slow, non-deterministic, or have uncontrollable side effects like external APIs or email sending.

When should I not write tests for a change?▼

Skip tests only for pure configuration changes, documentation updates, or static content with no behavioral impact. Any change to logic, behavior, or edge-case handling warrants a test.

Why do my tests break every time I refactor code?▼

Tests that assert on internal method calls or implementation details break during refactoring even when behavior is unchanged. Assert on inputs and outputs (state) instead of interaction sequences.

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