adversarial-test-design

adversarial-test-design is a skill for Claude Code, Codex from samuelgudi/iknowkungfu. It costs 58 tokens per session (1,354 once invoked), scanned A, original, MIT.

Guidance for designing tests that try to expose broken code rather than merely pass. It covers realistic inputs, avoiding misleading mocks, and proving a test fails for the intended reason.

In plain words
What is it for?
Use it when writing or reviewing tests for new features, bug fixes, or refactors, especially when existing tests pass but regressions still occur.
Why use it?
It reduces false confidence from tests that stay green even when the implementation is wrong.

Skill for Claude CodeCodex

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

Good fit Use it when writing or reviewing tests for new features, bug fixes, or refactors, especially when existing tests pass but regressions still occur.

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Install with agentmods
npx agentmods add skills/samuelgudi/iknowkungfu/adversarial-test-design
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 samuelgudi/iknowkungfu --skill adversarial-test-design
Clone the repo
git clone --depth 1 https://github.com/samuelgudi/iknowkungfu

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 adversarial-test-design

README.md
[![agentmods](https://agentmods.dev/badge/skills/samuelgudi/iknowkungfu/adversarial-test-design/github.svg)](https://agentmods.dev/skills/samuelgudi/iknowkungfu/adversarial-test-design)
Your own site
<a href="https://agentmods.dev/skills/samuelgudi/iknowkungfu/adversarial-test-design"><img src="https://agentmods.dev/badge/skills/samuelgudi/iknowkungfu/adversarial-test-design/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 adversarial-test-design

Your own site · 80×15
<a href="https://agentmods.dev/skills/samuelgudi/iknowkungfu/adversarial-test-design"><img src="https://agentmods.dev/badge/skills/samuelgudi/iknowkungfu/adversarial-test-design.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 58 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,354 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 $0.00058 $0.01354
Opus 5 $0.00029 $0.00677
Sonnet 5 $0.00012 $0.00271
Haiku 4.5 $0.00006 $0.00135

Measured 11d ago against content hash f0afce5c755f, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

adversarial-test-design 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/samuelgudi/adversarial-test-design/SKILL.md · 77 lines

How it starts

The opening of the file, as written. The whole thing — 77 lines — stays where its author put it; the contents beside it link to each section on GitHub.

adversarial-test-design

A test's job is to fail when the code is wrong. A test that passes whether or not the code is correct has done nothing — it is theatre that produces a green checkmark. This skill is about writing tests that genuinely try to break the code, so that a passing suite actually means something.

The mindset shift: do not write a test to confirm the code works. Write a test to catch the code being broken. Those produce different tests.

Use this skill when

  • You are writing tests for new code or a bug fix.
  • An existing suite is green but bugs still ship — a sign the tests are not biting.
  • You are reviewing tests and want to judge whether they would actually catch a regression.

Real-red before green

Before a test is worth anything, you must have seen it fail for the right reason.

  1. Write the test.
  2. Run it against code that is wrong — either the not-yet-written implementation, or the pre-fix buggy code for a bug-fix test. Watch it fail. Confirm it failed because of the behaviour you are testing, not because of a typo or a missing import.
  3. Now make it pass.

A test that has only ever been seen green is unverified. You do not know if it can fail at all. The single most common defect in a test suite is tests that cannot fail.

Adversarial inputs

The happy path is the input the author already had in mind — and the author already made that case work. Bugs live in the inputs the author did not think of. Deliberately reach for those:

  • Empty and absent — empty string, empty list, empty file, zero, null, missing optional field.
  • Boundaries — first, last, one past the end, exactly the limit, exactly one over.
  • Malformed — wrong type, wrong shape, truncated, trailing garbage, wrong encoding.
  • Large — input big enough to expose an O(n²), a buffer assumption, a recursion limit.
  • Hostile text — unicode, emoji, right-to-left, embedded quotes and separators, the characters that break naive parsing and naive escaping.
  • Concurrent / repeated — the same operation twice, two operations interleaved, retry after partial failure.
  • The input that violates an unstated assumption — for every "this will always be X" the code assumes, write the test where it is not X.

Read the full file on GitHub · 77 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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 · 77 lines · 58 tokens per session scan A f0afce5c755f

Subscribe to this mod's changes

adversarial-test-design is a skill published in the GitHub repository samuelgudi/iknowkungfu (2 stars, last pushed 1mo ago), licensed MIT. It adds 58 tokens to every session and 1,354 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.

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