Borrowing it
Nothing to install: this file belongs to kenn-io/kata. 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/kenn-io/kata/main/.claude/skills/testing-without-tautologies/SKILL.mdgit clone --depth 1 https://github.com/kenn-io/kataWrote 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/kenn-io/kata/testing-without-tautologies)<a href="https://agentmods.dev/skills/kenn-io/kata/testing-without-tautologies"><img src="https://agentmods.dev/badge/skills/kenn-io/kata/testing-without-tautologies.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 5.1 | $0.00053 | $0.02061 |
| Opus 5 | $0.00026 | $0.01030 |
| Sonnet 5 | $0.00011 | $0.00412 |
| Haiku 4.5 | $0.00005 | $0.00206 |
Grade A, and why
testing-without-tautologies 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 — 125 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Testing Without Tautologies
Core Idea
Tests should fail when protected behavior breaks. A passing test helps only if it can catch a real problem.
Before writing or changing a test, ask: "What production change should make this test fail?" If you cannot answer, redesign the test.
This pairs with the repo's Test First rule: the failing test you write before the implementation must fail because the behavior is missing, not because of a typo or an assertion on scaffolding. Watch it fail for the right reason.
Quality Gate
Before writing the test body, answer these:
- Who uses this? Prefer the HTTP API contract, CLI output and exit codes, persisted DB state, emitted events, rendered TUI, or caller-visible results. Avoid private state.
- What example proves it? Use concrete inputs and literal expected outputs. Do not compute expected values with production logic.
- What break would this catch? Name the wrong branch, missing side effect, wrong argument, boundary case, or contract violation.
- Do we own it? Test our choices at framework, SDK, database, and service boundaries. Do not re-test documented dependency mechanics.
- Can you state it? Given this setup, when the user/system does X, then Y observable behavior changes. If Y is not assertable, the test is not ready.
Required Checks
Apply these checks to every new or modified test:
-
Assert observable effects
- Check returned values, persisted rows, HTTP response bodies and status codes, emitted events (
/eventsNDJSON), CLI stdout/stderr/exit codes, rendered TUI output, errors, or auth outcomes. - A no-assertion test is acceptable only when the failure mode is the subject, such as "this constructor rejects invalid input." Prefer explicit assertions anyway.
- Check returned values, persisted rows, HTTP response bodies and status codes, emitted events (
-
Prefer real collaborators over doubles
- This repo is built for it:
internal/testenv.New(t)boots a real daemon over loopback TCP with a real SQLite store;internal/testfixprovides real git repos and.kata.tomlfixtures. Use them instead of hand-rolled fakes of the storage or daemon layers. - Reserve fakes for genuinely external boundaries (a remote hub, GitHub, an embedding provider) and for the TUI's client seam.
- This repo is built for it:
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 · 125 lines · 53 tokens per session scan A 4b205fa223fc
testing-without-tautologies is a skill published in the GitHub repository kenn-io/kata (415 stars, last pushed yesterday), licensed MIT. It adds 53 tokens to every session and 2,061 once invoked, about $0.0003 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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