devtools

cats – Auto‑generate resilient API fuzz tests with 1.4k+ GitHub stars

Name: cats – Auto‑generate resilient API fuzz tests with 1.4k+ GitHub stars
Author: Endava

Boost your OpenAPI reliability instantly; cats creates, runs, and reports self‑healing REST API fuzz tests without code—perfect for founders needing fast, low‑maintenance QA.

From the repo · “CATS is a REST API Fuzzer and negative testing tool for OpenAPI endpoints. CATS automatically generates, runs and reports tests with minimum configuration and no coding effort. Tests are self-healing and do not require maintenance.”

1,377 stars+1★ this week92 forksJavaGuide quality 8/10 · reviewed Oct 16Updated 10/20/2026100% free · open source

What it does

CATS automatically generates, runs, and reports tests for OpenAPI endpoints with minimal configuration and no coding effort, providing robust API testing and negative testing capabilities.

When to use it

•When you need to test OpenAPI endpoints without manually writing test cases
•When you want to ensure your API is resilient to unexpected input or edge cases
•When you need to reduce manual testing effort and maintenance for your API

Ready-to-paste prompt

java -jar target/cats-1.0.0.jar -c config.yml -e https://your-api-endpoint.com/openapi.json

Heads up: Ensure you have Java 11 or later installed on your system, as CATS requires this version to run

Saves to your device

Use with Claude

New

Skip the builder — one click puts this in Claude, Cursor, Antigravity and more.

✅ Light setup

Installs with a command or two; your AI agent can do it for you.

Try it instantly — no install

Claude Code

mkdir -p ~/.claude/skills/cats && curl -fsSL https://workflowstacks.com/api/skills/cats/claude-skill -o ~/.claude/skills/cats/SKILL.md

Open in another AI app

Opens the app with this repo with the prompt ready to go — no copy-paste needed.

Connect the whole catalog (MCP)

claude mcp add --transport http workflowstacks https://workflowstacks.com/api/mcp

Adds a WorkflowStacks connector to Claude Code: search and load any skill here by chatting.

Use with Claude

New

Skip the builder — one click puts this in Claude, Cursor, Antigravity and more.

✅ Light setup

Installs with a command or two; your AI agent can do it for you.

Try it instantly — no install

Claude Code

mkdir -p ~/.claude/skills/cats && curl -fsSL https://workflowstacks.com/api/skills/cats/claude-skill -o ~/.claude/skills/cats/SKILL.md

Open in another AI app

Opens the app with this repo with the prompt ready to go — no copy-paste needed.

Connect the whole catalog (MCP)

claude mcp add --transport http workflowstacks https://workflowstacks.com/api/mcp

Adds a WorkflowStacks connector to Claude Code: search and load any skill here by chatting.

Quick Actions

Details

Creator

Endava

Language

Java

Do this with a working workflow

Pages we wrote and tested that put a skill like this to work — importable n8n templates, outcome guides and Claude Desktop configs.

Outcome guide

Triage your inbox automatically

The workflow watches your inbox and classifies each new email by priority with a one-line reason and a draft reply, logging everything to a ranked sheet. You open your day to a triaged list, not a pile.

Outcome guide

Reduce meeting no-shows automatically

Keep your meetings in a Google Sheet. Every morning the workflow emails a warm, confirming reminder to anyone scheduled for the next day — automatically, in your voice.