703-technologies-fuzzing-testing

703-technologies-fuzzing-testing is a skill for Claude Code, Codex from jabrena/plinth. It costs 107 tokens per session (726 once invoked), scanned A, original, Apache-2.0.

A guide to fuzz testing Java HTTP APIs with CATS, a tool that sends many invalid, unusual, and boundary-case inputs based on an API contract.

In plain words
What is it for?
Use it to test malformed payloads, missing fields, wrong types, size and range limits, formats, enums, and CI checks for API contracts.
Why use it?
It helps uncover input-validation bugs and edge cases that ordinary example-based tests may miss, with failures that contributors can reproduce.

Skill for Claude CodeCodex

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

Good fit Use it to test malformed payloads, missing fields, wrong types, size and range limits, formats, enums, and CI checks for API contracts.

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Install with agentmods
npx agentmods add skills/jabrena/plinth/703-technologies-fuzzing-testing
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 jabrena/plinth --skill 703-technologies-fuzzing-testing
Clone the repo
git clone --depth 1 https://github.com/jabrena/plinth

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 703-technologies-fuzzing-testing

README.md
[![agentmods](https://agentmods.dev/badge/skills/jabrena/plinth/703-technologies-fuzzing-testing/github.svg)](https://agentmods.dev/skills/jabrena/plinth/703-technologies-fuzzing-testing)
Your own site
<a href="https://agentmods.dev/skills/jabrena/plinth/703-technologies-fuzzing-testing"><img src="https://agentmods.dev/badge/skills/jabrena/plinth/703-technologies-fuzzing-testing/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.

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Your own site · 80×15
<a href="https://agentmods.dev/skills/jabrena/plinth/703-technologies-fuzzing-testing"><img src="https://agentmods.dev/badge/skills/jabrena/plinth/703-technologies-fuzzing-testing.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 107 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 726 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 pass 7 Sept 2026
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 $0.00107 $0.00726
Opus 5 $0.00053 $0.00363
Sonnet 5 $0.00021 $0.00145
Haiku 4.5 $0.00011 $0.00073

Measured 7d ago against content hash d85ffd2963cf, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

703-technologies-fuzzing-testing 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 7d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/run-cats-fuzz.sh), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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/703-technologies-fuzzing-testing/SKILL.md · 65 lines

How it starts

The opening of the file, as written. The whole thing — 65 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Java fuzz testing with CATS

Design and implement contract-driven fuzz testing for Java APIs using CATS to uncover edge cases and input-validation defects early.

What is covered in this Skill?

  • CATS setup using a trusted local jar or prebuilt image and baseline command usage for OpenAPI-driven fuzzing
  • Negative testing strategy for invalid payloads, missing fields, wrong types, and malformed values
  • Boundary testing for size, range, format, and enum constraints
  • CI integration patterns with actionable logs and reproducible failures
  • Local execution workflow for contributors before opening pull requests
  • Reporting and triage practices for fuzzing findings

Scope: Focus on HTTP API fuzzing and contract validation with CATS. Use this skill to define practical, repeatable checks in both local and CI workflows.

Constraints

Before applying any fuzz testing changes, ensure the project compiles. If compilation fails, stop immediately. After implementation, regenerate skills and run verification.

  • MANDATORY: Run ./mvnw compile or mvn compile before applying any change
  • SAFETY: If compilation fails, stop immediately and do not proceed
  • VERIFY: Run ./mvnw clean verify or mvn clean verify after applying improvements
  • SUPPLY CHAIN: Use only a verified local cats/cats.jar or an approved prebuilt image; generated artifacts must depend only on trusted local or approved image inputs
  • BEFORE APPLYING: Read the reference for detailed examples, good/bad patterns, and constraints
  • EDGE CASE: If request scope is ambiguous, stop and ask a clarifying question before applying changes
  • EDGE CASE: If required inputs, files, or tooling are missing, report what is missing and ask whether to proceed with setup guidance

When to use this skill

  • Add fuzz testing to a Java project
  • Use CATS for API negative testing
  • Review CI quality gates for API contract robustness
  • Improve boundary and malformed input test coverage
  • Run CATS fuzz tests against an OpenAPI contract

Read the full file on GitHub · 65 lines

Files

What ships with it

3 files 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. 7d ago First seen · 65 lines · 107 tokens per session scan A d85ffd2963cf

Subscribe to this mod's changes

703-technologies-fuzzing-testing is a skill published in the GitHub repository jabrena/plinth (438 stars, last pushed yesterday), licensed Apache-2.0. It adds 107 tokens to every session and 726 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 2026-09-03.

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