prove-the-test-can-fail

prove-the-test-can-fail is a skill for Claude Code from iamakbarsha1/whetstone. It costs 106 tokens per session (1,058 once invoked), scanned A, original, CC-BY-4.0.

A way to verify that a test can detect the failure it is meant to catch. It temporarily breaks the code under test and checks that the intended assertion fails, while also checking that new branches can be reached by the test setup.

In plain words
What is it for?
Checking tests after writing them or before trusting a passing result. It helps validate assertions, mocks, fixtures, and branch coverage.
Why use it?
A test that only passes may be testing the wrong thing or may never exercise the new behavior. Making it fail on purpose exposes weak assertions and unreachable branches.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the whetstone plugin — 25 skills shipped together

Good fit Checking tests after writing them or before trusting a passing result. It helps validate assertions, mocks, fixtures, and branch coverage.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/iamakbarsha1/whetstone/prove-the-test-can-fail
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.

Any agent
npx skills add iamakbarsha1/whetstone --skill prove-the-test-can-fail
Clone the repo
git clone --depth 1 https://github.com/iamakbarsha1/whetstone

Made for: Claude Code.

Or install whetstone, the plugin that ships this one along with the rest of its 25 skills.

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 prove-the-test-can-fail

README.md
[![agentmods](https://agentmods.dev/badge/skills/iamakbarsha1/whetstone/prove-the-test-can-fail/github.svg)](https://agentmods.dev/skills/iamakbarsha1/whetstone/prove-the-test-can-fail)
Your own site
<a href="https://agentmods.dev/skills/iamakbarsha1/whetstone/prove-the-test-can-fail"><img src="https://agentmods.dev/badge/skills/iamakbarsha1/whetstone/prove-the-test-can-fail/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.

agentmods 80×15 button for prove-the-test-can-fail

Your own site · 80×15
<a href="https://agentmods.dev/skills/iamakbarsha1/whetstone/prove-the-test-can-fail"><img src="https://agentmods.dev/badge/skills/iamakbarsha1/whetstone/prove-the-test-can-fail.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 106 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,058 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin unknown No closer match found 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 5.1 $0.00106 $0.01058
Opus 5 $0.00053 $0.00529
Sonnet 5 $0.00021 $0.00212
Haiku 4.5 $0.00011 $0.00106

Measured 11d ago against content hash 86c603f775fc, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

prove-the-test-can-fail 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 11d 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.

skills/prove-the-test-can-fail/SKILL.md · 84 lines

The source is not reproduced here

Licensed CC-BY-4.0

The repository is licensed CC-BY-4.0, which this catalogue does not treat as permission to reproduce the file. Read it at the source.

Read it on GitHub

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. 11d ago First seen · 84 lines · 106 tokens per session scan A 86c603f775fc

Subscribe to this mod's changes

prove-the-test-can-fail is a skill published in the GitHub repository iamakbarsha1/whetstone (4 stars, last pushed 2d ago), licensed CC-BY-4.0. It adds 106 tokens to every session and 1,058 once invoked, about $0.0005 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.