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.
npx agentmods add skills/kaininx/plaintab/tddnpx skills add kaininx/PlainTab --skill tddgit clone --depth 1 https://github.com/kaininx/PlainTabWrote 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.
[](https://agentmods.dev/skills/kaininx/plaintab/tdd)<a href="https://agentmods.dev/skills/kaininx/plaintab/tdd"><img src="https://agentmods.dev/badge/skills/kaininx/plaintab/tdd.svg" alt="Measured on agentmods" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00037 | $0.00560 |
| Opus 5 | $0.00018 | $0.00280 |
| Sonnet 5 | $0.00007 | $0.00112 |
| Haiku 4.5 | $0.00004 | $0.00056 |
Grade A, and why
tdd 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 3d 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.
How it starts
The opening of the file, as written. The whole thing — 64 lines — stays where its author put it; the contents beside it link to each section on GitHub.
PlainTab TDD
Use this skill when changing runtime behavior. Adapted for PlainTab from Matt Pocock's tdd skill.
Philosophy
Tests should describe observable behavior through the public interface, not internal structure. In PlainTab, the public interface might be a runtime module API, a settings interaction, a stored config shape, a wallpaper source lifecycle, or the rendered new-tab page.
PlainTab has no package manager or test framework. Do not add one. Use focused Node scripts, browser automation, and existing validation commands.
Before Code
- Read
.claude/rules/00-core.mdand the relevant module rule. - Identify the behavior to lock down in user-facing language.
- Choose the smallest useful feedback loop:
- Node script in
docs/ai-tasks/for pure JS behavior. - Browser/Playwright check for DOM, settings, command palette, or wallpaper rendering.
- Manual web-mode check only when automation is not practical.
- Node script in
- Name the check after behavior, not implementation.
Red-Green Loop
Work one vertical slice at a time:
- RED: write one failing check for one behavior.
- Verify RED: run it and confirm it fails for the expected reason.
- GREEN: write the smallest production change to pass.
- Verify GREEN: run the check again.
- Repeat for the next behavior.
Do not write a batch of tests and then a batch of implementation. Do not refactor while RED.
PlainTab Test Shape
Good checks:
- Exercise real modules and real serialized config shapes.
- Preserve existing localStorage keys unless the task includes a migration.
- Cover extension/web-mode differences when the behavior depends on browser APIs.
- Assert visible wallpaper safety when touching image layers: at least one layer should remain visible.
- Assert language key completeness when adding UI copy.
Avoid:
- Adding npm, package.json, lint frameworks, test frameworks, or frontend frameworks.
- Tests that only assert private helper names or DOM implementation details unrelated to behavior.
- Long startup work in repro code that would never exist in the real first-paint path.
What ships with it
1 file 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.
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.
- 3d ago First seen · 64 lines · 37 tokens per session scan A a682a128f7c2
tdd is a skill published in the GitHub repository kaininx/PlainTab (88 stars, last pushed 3mo ago), licensed MIT. It adds 37 tokens to every session and 560 once invoked, about $0.0002 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.
Other skills, from other repositories
engram-testing-coverage
TDD and coverage standards for Engram. Trigger: When implementing behavior changes in any package.
tdd
Test-driven development. Use when the user wants to build features or fix bugs test-first, mentions "red-green-refactor", or wants integration tests.
test-first-bugs
Enforces a test-driven bug-fixing workflow. Use when a user reports a bug, failing code, an error, or asks to fix something.
mobiai-mobile-tdd
You MUST use this before writing any implementation code for a mobile feature, bug fix, refactor, or behavior change. Tests come before implementation — no exceptions.
white-box-red-testing
Find bugs by writing tests that should pass but don't. Invoke manually on user-chosen scope (commits, files, or coverage threshold). Outputs red tests with structured rationale. Use when user asks to "stress-test", "find bugs in", "attack", or "break" code.
refine-plan
Iteratively refine development plans using TDD methodology. Ensures plans are clear, actionable, and include red-green-refactor cycles with proper test coverage.