verification-beyond-tests

verification-beyond-tests is a skill for Claude Code, Codex from telus-labs/stagecraft. It costs 67 tokens per session (2,208 once invoked), scanned A, original, MIT.

A verification process that checks suitable code with property-based testing, mutation testing, or formal verification after ordinary tests pass. Property-based testing tries many generated inputs, mutation testing checks whether tests detect deliberate defects, and formal verification proves selected rules where possible.

In plain words
What is it for?
Use it after a QA pass when a code change contains pure functions, important business rules, custom formatters, or state machines worth checking more deeply.
Why use it?
Passing example-based tests only shows that the tested examples work. This process looks for missed cases and weak tests, while recognizing that not every part of a program can be formally verified.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Needs its repository: it reads a path above its own folder, which exists only inside the repository. The line is import { encode, decode } from '../../url-codec';.

Good fit Use it after a QA pass when a code change contains pure functions, important business rules, custom formatters, or state machines worth checking more deeply.

Compare 6 skills from other repositories ↓
Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo
git clone --depth 1 https://github.com/telus-labs/stagecraft
agentmods
npx agentmods add skills/telus-labs/stagecraft/verification-beyond-tests

Made for: Claude Code, Codex.

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 verification-beyond-tests

README.md
[![agentmods](https://agentmods.dev/badge/skills/telus-labs/stagecraft/verification-beyond-tests/github.svg)](https://agentmods.dev/skills/telus-labs/stagecraft/verification-beyond-tests)
Your own site
<a href="https://agentmods.dev/skills/telus-labs/stagecraft/verification-beyond-tests"><img src="https://agentmods.dev/badge/skills/telus-labs/stagecraft/verification-beyond-tests/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 verification-beyond-tests

Your own site · 80×15
<a href="https://agentmods.dev/skills/telus-labs/stagecraft/verification-beyond-tests"><img src="https://agentmods.dev/badge/skills/telus-labs/stagecraft/verification-beyond-tests.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 67 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,208 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. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 1 finding, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • medium MCP Rug Pull · line 110
    npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.
    Fix: Pin the version: npx @scope/[email protected]
How audits are shown
Origin original 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 $0.00067 $0.02208
Opus 5 $0.00034 $0.01104
Sonnet 5 $0.00013 $0.00442
Haiku 4.5 $0.00007 $0.00221

Measured 9d ago against content hash b480bf6f8799, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

verification-beyond-tests 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.

skills/verification-beyond-tests/SKILL.md · 202 lines

How it starts

The opening of the file, as written. The whole thing — 202 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Verification beyond tests — five phases

Unit tests prove the cases the author thought of. The cases nobody thought of remain unverified. This skill applies systematic verification methods to make the unverified surface smaller — without pretending to verify things that aren't verifiable.

When to use

You're authoring stage-06d (verifier role). Stage-06 (qa) already returned PASS — the floor is in place. The track is full, so the expectation is rigour over speed. Your task: pick the right method per candidate, apply it, surface findings.

Phase 1 — Inventory candidates

Scan the diff. For each function/module, classify against the methods:

Code shape Method
Pure functions over structured data — parsers, validators, codecs, transforms, sort/dedupe, math, normalisation Property-based
Custom formatters, serializers, or encoders over user-controlled data — logging formatters, structured log schemas, metric label builders, trace attribute setters Property-based (valid-output invariant: output is parseable/well-formed for all inputs up to the field's documented max)
Critical business logic with example tests — auth, billing, anything with a real test suite Mutation
Concurrent state machines, distributed protocols, consistency invariants, security properties Formal
Glue, UI, CRUD with thin logic Skip with reason

Write the inventory as a table in the report. Be honest about glue — applying mutation to a thin CRUD wrapper produces theatre, not signal.

Caution on the "glue" classification for observability code. Logging formatters and structured log helpers look like glue but are serializers over user-controlled input. Python's logging.Handler.emit(), Go's slog handlers, Java's Appender.append(), and equivalent frameworks catch formatter exceptions internally — a NameError, KeyError, or encoding error in the formatter is written to stderr and the application continues normally. HTTP-response tests cannot detect this failure mode; the service returns correct responses while silently dropping every log line. Classify custom log formatters as codecs, not glue. The property to assert is the valid-output invariant: for all inputs up to the field's max length, the formatted output must be parseable by the target consumer.

Read the full file on GitHub · 202 lines

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. 9d ago First seen · 202 lines · 67 tokens per session scan A b480bf6f8799

Subscribe to this mod's changes

verification-beyond-tests is a skill published in the GitHub repository telus-labs/stagecraft (6 stars, last pushed 3d ago), licensed MIT. It adds 67 tokens to every session and 2,208 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 2026-08-31.

Related

Other skills, from other repositories

intuitive-tests

Use this skill whenever the user asks about unit test best practices, test organization, flat test suites, redundant tests, test refactors, pytest/JUnit/Jest/xUnit layout, test taxonomy, flaky tests, coverage quality, fixtures, mocks, parametrization, pruning existing UTs, or "which tests are worth keeping." It…

MiaoDX/intuitive-flow · 154 tokens

verify

Run the HUMHUM quality gates that are actually touched by the current diff — frontend typecheck + vitest, and Rust fmt/clippy/test — mirroring CI. Use before marking work done, opening a PR, or when asked to "verify", "check", or "run the gates".

edible999999999-jpg/humhum · 62 tokens

test-generation

Generate comprehensive tests for code including unit tests, integration tests, and edge case coverage. Analyzes code to identify testable units and generates tests matching the project's testing framework and conventions.

richardcb/oh-my-gemini · 41 tokens

foundry-hosted-agent-validation

Step-by-step process for validating a Python Foundry hosted agent sample (under python/samples/04-hosting/foundry-hosted-agents/) end to end — running it locally (native runtime and azd ai agent run) and after deploying it to an Azure AI Foundry project with azd. Use this when asked to validate a hosted agent sample.

microsoft/agent-framework · 82 tokens

build-and-test

How to build and test .NET projects in the Agent Framework repository. Use this when verifying or testing changes.

microsoft/agent-framework · 26 tokens

writing-tests

Write unit tests, component tests, and integration tests for AiderDesk using Vitest and React Testing Library. Use when creating new tests, adding test coverage, configuring mocks, setting up test files, or debugging failing tests.

hotovo/aider-desk · 48 tokens