tdd-workflow

tdd-workflow is a skill for Claude Code, Codex from diillson/chatcli. It costs 21 tokens per session (724 once invoked), scanned A, a copy of tdd-workflow, Apache-2.0.

A set of Test-Driven Development (TDD) practices, where you write a failing test, make it pass with the simplest code, then improve the code.

In plain words
What is it for?
It helps plan tests for normal cases, edge cases, and errors while guiding the RED-GREEN-REFACTOR cycle.
Why use it?
It gives development a repeatable sequence and keeps new code tied to clearly stated behaviour.

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/diillson/chatcli/tdd-workflow
Any agent
npx skills add diillson/chatcli --skill tdd-workflow
Clone the repo
git clone --depth 1 https://github.com/diillson/chatcli

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 tdd-workflow

README.md
[![agentmods](https://agentmods.dev/badge/skills/diillson/chatcli/tdd-workflow.svg)](https://agentmods.dev/skills/diillson/chatcli/tdd-workflow)
Your own site
<a href="https://agentmods.dev/skills/diillson/chatcli/tdd-workflow"><img src="https://agentmods.dev/badge/skills/diillson/chatcli/tdd-workflow.svg" alt="Measured on agentmods" height="20"></a>
Per session 21 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 724 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 91% copy Near-identical to another mod 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 $0.00021 $0.00724
Opus 5 $0.00010 $0.00362
Sonnet 5 $0.00004 $0.00145
Haiku 4.5 $0.00002 $0.00072

Measured yesterday against content hash b8fceb81c096, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

tdd-workflow 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 yesterday.

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.

Origin

This is a copy

91% identical to tdd-workflow — 2 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.agent/skills/tdd-workflow/SKILL.md · 150 lines

How it starts

The opening of the file, as written. The whole thing — 150 lines — stays where its author put it; the contents beside it link to each section on GitHub.

TDD Workflow

Write tests first, code second.


1. The TDD Cycle

🔴 RED → Write failing test
    ↓
🟢 GREEN → Write minimal code to pass
    ↓
🔵 REFACTOR → Improve code quality
    ↓
   Repeat...

2. The Three Laws of TDD

  1. Write production code only to make a failing test pass
  2. Write only enough test to demonstrate failure
  3. Write only enough code to make the test pass

3. RED Phase Principles

What to Write

Focus Example
Behavior "should add two numbers"
Edge cases "should handle empty input"
Error states "should throw for invalid data"

RED Phase Rules

  • Test must fail first
  • Test name describes expected behavior
  • One assertion per test (ideally)

4. GREEN Phase Principles

Minimum Code

Principle Meaning
YAGNI You Aren't Gonna Need It
Simplest thing Write the minimum to pass
No optimization Just make it work

GREEN Phase Rules

  • Don't write unneeded code
  • Don't optimize yet
  • Pass the test, nothing more

5. REFACTOR Phase Principles

What to Improve

Area Action
Duplication Extract common code
Naming Make intent clear
Structure Improve organization
Complexity Simplify logic

REFACTOR Rules

  • All tests must stay green
  • Small incremental changes
  • Commit after each refactor

6. AAA Pattern

Every test follows:

Step Purpose
Arrange Set up test data
Act Execute code under test
Assert Verify expected outcome

7. When to Use TDD

Scenario TDD Value
New feature High
Bug fix High (write test first)
Complex logic High
Exploratory Low (spike, then TDD)
UI layout Low

8. Test Prioritization

Priority Test Type
1 Happy path
2 Error cases
3 Edge cases
4 Performance

Read the full file on GitHub · 150 lines

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. yesterday First seen · 150 lines · 21 tokens per session scan A b8fceb81c096

Subscribe to this mod's changes

tdd-workflow is a skill published in the GitHub repository diillson/chatcli (90 stars, last pushed today), licensed Apache-2.0. It adds 21 tokens to every session and 724 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 91% identical to tdd-workflow, differing in 2 lines, and is treated as a copy.