test-driven-development

test-driven-development is a skill for Claude Code, Codex from coctostan/pi-superpowers-plus. It costs 17 tokens per session (1,950 once invoked), scanned A, original, MIT.

A software development method called test-driven development, or TDD, where you write a test before writing the code it checks. You then make the smallest code change that passes the test and improve it afterward.

In plain words
What is it for?
Use it when adding features, fixing bugs, changing tested code, or working on code without existing tests.
Why use it?
It helps catch mistakes early and keeps new behavior tied to a clear, repeatable check.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/coctostan/pi-superpowers-plus/test-driven-development
Any agent
npx skills add coctostan/pi-superpowers-plus --skill test-driven-development
Clone the repo
git clone --depth 1 https://github.com/coctostan/pi-superpowers-plus

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for test-driven-development

README.md
[![agentmods](https://agentmods.dev/badge/skills/coctostan/pi-superpowers-plus/test-driven-development.svg)](https://agentmods.dev/skills/coctostan/pi-superpowers-plus/test-driven-development)
Your own site
<a href="https://agentmods.dev/skills/coctostan/pi-superpowers-plus/test-driven-development"><img src="https://agentmods.dev/badge/skills/coctostan/pi-superpowers-plus/test-driven-development.svg" alt="Measured on agentmods" height="20"></a>
Per session 17 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,950 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00017 $0.01950
Opus 5 $0.00009 $0.00975
Sonnet 5 $0.00003 $0.00390
Haiku 4.5 $0.00002 $0.00195

Measured 4d ago against content hash f0bb91194955, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

test-driven-development scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 4d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/test-driven-development/SKILL.md · 256 lines

How it starts

The opening of the file, as written. The whole thing — 256 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Related skills: Before claiming done, use /skill:verification-before-completion to verify tests actually pass.

Test-Driven Development (TDD)

Overview

Write the test first. Watch it fail. Write minimal code to pass.

Core principle: If you didn't watch the test fail, you don't know if it tests the right thing.

Violating the letter of the rules is violating the spirit of the rules.

Prerequisites

  • Active branch (not main) or user-confirmed intent to work on main
  • Approved plan or clear task scope

When to Use — Three Scenarios

Not every change requires the same TDD approach. Determine which scenario applies:

Scenario 1: New Feature / New File

Full TDD cycle. No shortcuts.

  1. Write a failing test
  2. Watch it fail
  3. Write minimal code to pass
  4. Watch it pass
  5. Refactor
  6. Repeat

This is the default. If in doubt, use this scenario.

Scenario 2: Modifying Code with Existing Tests

When changing code that already has test coverage:

  1. Run existing tests — confirm green
  2. Make your change
  3. Run tests again — confirm still green
  4. If your change isn't covered by existing tests, add a test for it
  5. If existing tests already cover the changed behavior, you're done

Key: You must verify existing tests pass before and after your change. If you can't confirm test coverage, fall back to Scenario 1.

Scenario 3: Trivial Change

For typo fixes, config tweaks, string changes, renames:

  • Use judgment
  • If relevant tests exist, run them after your change
  • Don't write a new test for a string literal change

Be honest: If the change touches logic, it's not trivial. Use Scenario 1 or 2.

Interpreting Runtime Warnings

The workflow monitor tracks your TDD phase and may inject warnings like:

⚠️ TDD: Writing source code (src/foo.ts) without a failing test.

When you see this, pause and assess:

  • Which scenario applies to this change?
  • If Scenario 2: run existing tests to confirm coverage, then proceed
  • If Scenario 1: write a failing test first
  • If Scenario 3: proceed, run tests after

Read the full file on GitHub · 256 lines

Files

What ships with it

4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 4d ago First seen · 256 lines · 17 tokens per session scan A f0bb91194955

Subscribe to this mod's changes

test-driven-development is a skill published in the GitHub repository coctostan/pi-superpowers-plus (104 stars, last pushed 6mo ago), licensed MIT. It adds 17 tokens to every session and 1,950 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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