Borrowing it
Nothing to install: this file belongs to mrlarson2007/copilot-tdd-harness. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/mrlarson2007/copilot-tdd-harness/master/.github/skills/tdd-planning/SKILL.mdgit clone --depth 1 https://github.com/mrlarson2007/copilot-tdd-harnessWrote 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/mrlarson2007/copilot-tdd-harness/tdd-planning)<a href="https://agentmods.dev/skills/mrlarson2007/copilot-tdd-harness/tdd-planning"><img src="https://agentmods.dev/badge/skills/mrlarson2007/copilot-tdd-harness/tdd-planning/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/mrlarson2007/copilot-tdd-harness/tdd-planning"><img src="https://agentmods.dev/badge/skills/mrlarson2007/copilot-tdd-harness/tdd-planning.svg" alt="Reviewed on agentmods" width="80" 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 5.1 | $0.00045 | $0.00684 |
| Opus 5 | $0.00023 | $0.00342 |
| Sonnet 5 | $0.00009 | $0.00137 |
| Haiku 4.5 | $0.00005 | $0.00068 |
Grade A, and why
tdd-planning 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 9d 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 — 95 lines — stays where its author put it; the contents beside it link to each section on GitHub.
TDD Planning Skill
Use this skill before the first RED cycle and again between cycles when the next behavior is not already obvious.
This skill is for planning only. It should not write production code, write tests, or execute a RED -> GREEN cycle.
Purpose
Help the agent think like a strong software engineer using TDD:
- clarify what the user actually wants
- identify candidate behaviors from a feature request
- prefer edge cases before happy path when appropriate
- choose the smallest falsifiable next slice
- decide whether the request is concrete enough to start RED
- when creating a test plan, use Given, When, Then format to specify each behavior and its expected outcome
Clarification Rules
Stop and ask exactly one focused question when the request is still too ambiguous to support a meaningful failing test.
Treat the request as too ambiguous when any of the following are true:
- it names a category but not a specific behavior
- it names multiple plausible behaviors without a clear first slice
- choosing the next test would require guessing inputs, outputs, or scope
Do not self-resolve category-level ambiguity just because one option looks smallest.
Treat category-level requests as mandatory clarification points even if one
candidate looks like the narrowest path. For example, "add another arithmetic
subcommand" requires a question; do not assume subtract, multiply, or any
other operation just to keep moving.
Do not use phrases like "assuming the new subcommand is...", "to proceed autonomously", or "I can pick the smallest behavior" when the request is still ambiguous. Ask the focused question instead and wait.
Planning Rubric
When multiple candidate behaviors are available, prefer the one that best fits this order:
- Can be described as one externally visible behavior
- Can be proven by one failing test
- Protects an edge case or risky boundary first, when that makes sense
- Requires the smallest production change that still moves the feature forward
- Leaves room for obvious follow-up cycles without speculative design
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.
- 9d ago First seen · 95 lines · 45 tokens per session scan A 05e8fcafab83
tdd-planning is a skill published in the GitHub repository mrlarson2007/copilot-tdd-harness (5 stars, last pushed 3mo ago), licensed MIT. It adds 45 tokens to every session and 684 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 2026-08-31.
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