tester-mindset

tester-mindset is a skill for Claude Code, Codex from n-n-code/n-n-code-skills. It costs 88 tokens per session (2,743 once invoked), scanned A, original, MIT.

A testing workflow for planning and reviewing tests in context. It covers acceptance criteria, edge cases, failure modes, exploratory testing, and whether evidence really supports a claim.

In plain words
What is it for?
Use it to design test plans, validation strategies, and acceptance criteria; find weak tests and missing edge cases; and judge whether a demo, metric, or test result is sufficient evidence.
Why use it?
It helps replace vague statements such as “this works” with checks that can show what happened. It also exposes tests that only repeat the claim without proving it.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/n-n-code/n-n-code-skills/tester-mindset
Any agent
npx skills add n-n-code/n-n-code-skills --skill tester-mindset
Clone the repo
git clone --depth 1 https://github.com/n-n-code/n-n-code-skills

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 tester-mindset

README.md
[![agentmods](https://agentmods.dev/badge/skills/n-n-code/n-n-code-skills/tester-mindset.svg)](https://agentmods.dev/skills/n-n-code/n-n-code-skills/tester-mindset)
Your own site
<a href="https://agentmods.dev/skills/n-n-code/n-n-code-skills/tester-mindset"><img src="https://agentmods.dev/badge/skills/n-n-code/n-n-code-skills/tester-mindset.svg" alt="Measured on agentmods" height="20"></a>
Per session 88 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,743 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00088 $0.02743
Opus 5 $0.00044 $0.01372
Sonnet 5 $0.00018 $0.00549
Haiku 4.5 $0.00009 $0.00274

Measured 4d ago against content hash f17fcecdbd8d, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

tester-mindset 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 4d 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.

.agents/skills/tester-mindset/SKILL.md · 277 lines

How it starts

The opening of the file, as written. The whole thing — 277 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Tester Mindset

A test is a small, deliberate meeting with consequence, arranged so truth can arrive before ruin does.

Use this as an orthogonal workflow skill. Compose it with implementation, review, security, product, or documentation skills when the main job is to make confidence earn its keep.

When To Use

  • design a test plan, validation strategy, QA approach, or acceptance criteria
  • identify edge cases, failure modes, adversarial cases, or missing evidence
  • decide whether existing tests, metrics, benchmarks, or demos prove enough
  • plan or debrief exploratory testing, chartered sessions, or bug hunts
  • review test quality and detect weak, tautological, or proof-theater tests
  • turn a vague claim such as "this works" into observable checks
  • review a change through the question "what consequence was invited?"

Not For

  • simply running an existing test command
  • broad debugging when the failure is already reproduced and the next step is diagnosis
  • security exploit analysis that needs the full security workflow
  • routine implementation work where ordinary repo validation is enough

Core Workflow

  1. Map the context. Identify the mission, stakeholders, risks, constraints, team skills, available evidence, and cost of being wrong. There are no universal testing best practices, only practices that fit a context.
  2. Name the claim. State the belief being tested in falsifiable language. If the claim is vague, split it into behavior, contract, performance, safety, usability, security, trust, maintenance, or process claims.
  3. Separate testing from checking. Checking applies explicit pass/fail rules to known expectations. Testing is investigation: learning, modeling, exploring, questioning, and interpreting. Automate checks, but do not pretend automation replaces judgment.
  4. Invite consequence. Ask what result would disappoint, disprove, embarrass, or force a change in behavior. If no outcome can change the conclusion, this is a ritual, not a test.
  5. Choose a survivable scale. Make the test strong enough to teach and small enough to survive. Prefer cheap probes first, then increase fidelity where risk, irreversibility, or user harm justifies it.
  6. Choose oracles deliberately. Name how a problem would be recognized: requirements, prior behavior, comparable products, standards, stakeholder expectations, user goals, internal consistency, product purpose, statutes, or expert judgment. Treat every oracle as fallible.
  7. Inspect the apparatus. Question fixtures, mocks, datasets, metrics, timing, environments, prompts, observers, and definitions of "pass." A failing test may expose a broken question, not only a broken system. Ask whether the fixture, mock, metric, benchmark, prompt, dataset, or environment is the thing actually being validated.
  8. Let reality disagree. Include paths that can contradict the preferred story: boundary data, malformed input, slow dependencies, retries, concurrency, time, state transitions, upgrade paths, human behavior, adversarial pressure, or conflicting stakeholder values.
  9. Interpret narrowly. Say what the result proves, what it only suggests, who it matters to, and what remains untouched. Passing evidence reduces uncertainty; it does not convert partial coverage into certainty.
  10. Choose the next consequence. If risk remains material, recommend the next smallest higher-fidelity check: integration test, exploratory session, benchmark, canary, monitoring, user trial, chaos probe, manual smoke, or review.

Read the full file on GitHub · 277 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. 4d ago First seen · 277 lines · 88 tokens per session scan A f17fcecdbd8d

Subscribe to this mod's changes

tester-mindset is a skill published in the GitHub repository n-n-code/n-n-code-skills (4 stars, last pushed 6d ago), licensed MIT. It adds 88 tokens to every session and 2,743 once invoked, about $0.0004 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.