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 skills add imMamdouhaboammar/get-fable --skill fable-tddgit clone --depth 1 https://github.com/imMamdouhaboammar/get-fableWrote 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/immamdouhaboammar/get-fable/fable-tdd)<a href="https://agentmods.dev/skills/immamdouhaboammar/get-fable/fable-tdd"><img src="https://agentmods.dev/badge/skills/immamdouhaboammar/get-fable/fable-tdd/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/immamdouhaboammar/get-fable/fable-tdd"><img src="https://agentmods.dev/badge/skills/immamdouhaboammar/get-fable/fable-tdd.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 | $0.00133 | $0.02021 |
| Opus 5 | $0.00067 | $0.01010 |
| Sonnet 5 | $0.00027 | $0.00404 |
| Haiku 4.5 | $0.00013 | $0.00202 |
Grade A, and why
fable-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 7d 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 — 231 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Fable TDD
Prove the behavior is missing or broken before changing production code, then make the smallest change that satisfies the right test at the right level.
Mission
TDD is not "write any failing test first." The red state must demonstrate the intended behavior gap through a trustworthy harness. A syntax error, broken fixture, stale build, or mock-only expectation does not earn the right to change production code.
The Skill optimizes for three things:
- causal confidence: the test fails because the behavior is wrong;
- minimal intervention: implementation changes only what the behavior requires;
- durable regression proof: the test would catch the bug if it returned.
Activate When
- fixing a reproducible bug or regression;
- adding behavior with a stable enough contract to assert;
- changing validation, state transitions, calculations, API behavior, persistence, or integration semantics;
- refactoring where an invariant needs executable characterization first.
Do Not Activate When
- the behavior cannot yet be located or reproduced (
fable-discover); - the main uncertainty is external API semantics (
fable-research); - the change is non-executable docs/metadata with no meaningful behavior test (
fable-execute); - the required test harness is itself broken or executing stale artifacts (
fable-recover).
Change Classification
Classify the behavior before choosing a test.
| Class | Preferred proof |
|---|---|
| Pure/domain logic | focused unit/property test |
| Boundary validation/error mapping | unit or contract test at boundary |
| Cross-module interaction | integration test through the changed contract |
| Database/queue/cache behavior | integration test with realistic boundary where feasible |
| HTTP/CLI/public API | contract/integration test at public entry point |
| UI user flow | component/integration first; E2E for high-value cross-boundary behavior |
| Concurrency/timing | deterministic coordination test, not sleep-and-hope |
| Legacy behavior with poor seams | characterization test at nearest stable boundary |
| Refactor/no intended behavior change | characterization/invariant tests before movement |
What ships with it
7 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.
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.
- 7d ago First seen · 231 lines · 133 tokens per session scan A c15ce7c9e62e
fable-tdd is a skill published in the GitHub repository imMamdouhaboammar/get-fable (4 stars, last pushed today), licensed MIT. It adds 133 tokens to every session and 2,021 once invoked, about $0.0007 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 2026-09-05.
Other skills, from other repositories
tdd
Test-driven development with red-green-refactor loop. Use when user wants to build features or fix bugs using TDD, mentions "red-green-refactor", wants integration tests, or asks for test-first development.
workflow-patterns
Use this skill when implementing tasks according to Conductor's TDD workflow, handling phase checkpoints, managing git commits for tasks, or understanding the verification protocol.
engineering-workflow
A Chinese-language workflow for reliable software development. It describes exploring the problem, making a plan, using TDD (test-driven development, where tests are written before the code), debugging methodically, reviewing code, and verifying the result.
implement
Implement a technical design by decomposing it into dependency-ordered vertical slices, executing each with TDD red-green, reviewing each via an isolated sub-agent, and persisting progress to a state file so work survives session restarts. Use when the user has a tech design (doc or settled conversation) and says…
principle-test-behavior-not-implementation
Apply when you write, change, or keep a test. Call the code the way its users do and assert the result they observe against a literal expected value. If the test would still pass when every imported function returns undefined, rewrite the assertion or delete the test.
test-driven-development
TDD: enforce RED-GREEN-REFACTOR, tests before code.