assumption-test

assumption-test is a skill for Claude Code from Neeeophytee/finding-unknowns-skills. It costs 50 tokens per session (456 once invoked), scanned A, original, MIT.

A method for testing an important technical assumption with a small, repeatable experiment. It turns uncertainty about software behavior, an integration, or data into a prediction that evidence can support or disprove.

In plain words
What is it for?
Use it to investigate runtime behavior, provider integrations, data handling, or other questions that code inspection alone cannot settle.
Why use it?
It prevents a plan from depending on an unverified belief that could later force a costly redesign. It also distinguishes a failed test from an experiment that was never run or was inconclusive.

Skill for Claude Code

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

Part of the finding-unknowns plugin — 13 skills shipped together

Good fit Use it to investigate runtime behavior, provider integrations, data handling, or other questions that code inspection alone cannot settle.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/neeeophytee/finding-unknowns-skills/assumption-test
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 Neeeophytee/finding-unknowns-skills --skill assumption-test
Clone the repo
git clone --depth 1 https://github.com/Neeeophytee/finding-unknowns-skills

Made for: Claude Code.

Or install finding-unknowns, the plugin that ships this one along with the rest of its 13 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 assumption-test

README.md
[![agentmods](https://agentmods.dev/badge/skills/neeeophytee/finding-unknowns-skills/assumption-test/github.svg)](https://agentmods.dev/skills/neeeophytee/finding-unknowns-skills/assumption-test)
Your own site
<a href="https://agentmods.dev/skills/neeeophytee/finding-unknowns-skills/assumption-test"><img src="https://agentmods.dev/badge/skills/neeeophytee/finding-unknowns-skills/assumption-test/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 assumption-test

Your own site · 80×15
<a href="https://agentmods.dev/skills/neeeophytee/finding-unknowns-skills/assumption-test"><img src="https://agentmods.dev/badge/skills/neeeophytee/finding-unknowns-skills/assumption-test.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 50 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 456 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 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 $0.00050 $0.00456
Opus 5 $0.00025 $0.00228
Sonnet 5 $0.00010 $0.00091
Haiku 4.5 $0.00005 $0.00046

Measured 2d ago against content hash 65aae0c9f8e8, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

assumption-test 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 2d 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/assumption-test/SKILL.md · 24 lines

How it starts

The opening of the file, as written. The whole thing — 24 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Assumption test

A plausible assumption can survive every planning conversation and still fail on contact with the system. Turn the consequential uncertainty into a question an experiment can answer.

Steps

  1. Read the request, relevant code, and existing evidence. If inspection already settles the question, cite that evidence and stop; do not manufacture an experiment. If several assumptions remain, select the one whose failure would most change the approach.
  2. State the assumption as an observable prediction. Define what would refute it, what would support it within the tested scope, and what would leave it inconclusive. Set those criteria before observing the result.
  3. Design the smallest discriminating experiment. Use an isolated fixture or test environment, the real component under question where available, and a bounded number of operations. Name what the setup cannot represent; a mock's behavior is not evidence about its provider.
  4. Run the experiment within the user's authorized scope. Preserve the command, relevant inputs, actual output, and environment details needed to reproduce it. If a tool or dependency is unavailable, report the experiment as unrun or inconclusive, with the missing prerequisite.
  5. Close with the assumption, method, observation, verdict (supported within scope, refuted, or inconclusive), and the planning decision this evidence changes. Recommend the next discriminating check only if it could change that decision. Keep temporary code separate from the production implementation.

Guardrails

  • One successful trial does not establish a universal claim. State the tested conditions and remaining uncertainty, particularly for concurrency and performance.
  • Do not use production writes, real payments, destructive operations, or newly incurred costs without authorization. An experiment does not grant additional permissions.
  • Distinguish the component failing from the experiment failing to run. Never turn missing access or a broken fixture into a verdict about the system.
  • Do not fix the implementation or broaden into a build unless the user requested it. The deliverable is evidence that informs a decision.

Read the full file on GitHub · 24 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. 2d ago First seen · 24 lines · 50 tokens per session scan A 65aae0c9f8e8

Subscribe to this mod's changes

assumption-test is a skill published in the GitHub repository Neeeophytee/finding-unknowns-skills (329 stars, last pushed 3d ago), licensed MIT. It adds 50 tokens to every session and 456 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 2026-09-09.

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