# harness-writing

> Designs and improves fuzzing harnesses for C/C++ and Rust.

Designs and improves fuzzing harnesses for C/C++ and Rust. Covers mapping raw bytes onto a target API, generating structured inputs, avoiding non-determinism and false crashes, and deciding what to fuzz together. Use when writing a first LLVMFuzzerTestOneInput or fuzz_target! harness, when a campaign finds nothing or reports crashes that will not reproduce, or when the target API needs structured rather than raw input.

- Type: Skill
- Made by: trailofbits
- Category: Developer tools
- Formats: Skills
- Version: 7b497d2
- Source: https://github.com/trailofbits/skills/tree/HEAD/plugins/testing-handbook-skills/skills/harness-writing
- Page: https://pluginboard.ai/skills/harness-writing

## Works with

- ChatGPT
- Claude
- Gemini
- GitHub Copilot
- Cursor
- Claude Code
- Codex
- Antigravity
- Gemini CLI
- Replit
- OpenClaw
- OpenCode
- Hermes Agent

## Install

### ChatGPT

In ChatGPT: Download the harness-writing folder and zip it, then Plugins → Skills → Create → Upload from your computer. Business and Enterprise plans.

View the folder on GitHub: https://github.com/trailofbits/skills/tree/HEAD/plugins/testing-handbook-skills/skills/harness-writing

### Claude

In Claude (web or desktop): Download the harness-writing folder and zip the folder itself, then upload it in Customize → Skills.

View the folder on GitHub: https://github.com/trailofbits/skills/tree/HEAD/plugins/testing-handbook-skills/skills/harness-writing

### Gemini

In Gemini: Download the harness-writing folder, then at gemini.google.com click Customize → Skills → Create → Upload and pick the folder (or a .zip of it).

View the folder on GitHub: https://github.com/trailofbits/skills/tree/HEAD/plugins/testing-handbook-skills/skills/harness-writing

### GitHub Copilot

Run in your terminal:

```shell
npx -y degit trailofbits/skills/plugins/testing-handbook-skills/skills/harness-writing ~/.copilot/skills/harness-writing
```

View the folder on GitHub: https://github.com/trailofbits/skills/tree/HEAD/plugins/testing-handbook-skills/skills/harness-writing

### Cursor

Run in your terminal:

```shell
npx -y degit trailofbits/skills/plugins/testing-handbook-skills/skills/harness-writing ~/.cursor/skills/harness-writing
```

View the folder on GitHub: https://github.com/trailofbits/skills/tree/HEAD/plugins/testing-handbook-skills/skills/harness-writing

### Claude Code

Run in your terminal:

```shell
npx -y degit trailofbits/skills/plugins/testing-handbook-skills/skills/harness-writing ~/.claude/skills/harness-writing
```

View the folder on GitHub: https://github.com/trailofbits/skills/tree/HEAD/plugins/testing-handbook-skills/skills/harness-writing

Or all of Testing Handbook Skills, in Claude Code:

```text
/plugin marketplace add trailofbits/skills
/plugin install testing-handbook-skills@trailofbits
```

### Codex

Run in your terminal:

```shell
npx -y degit trailofbits/skills/plugins/testing-handbook-skills/skills/harness-writing ~/.agents/skills/harness-writing
```

View the folder on GitHub: https://github.com/trailofbits/skills/tree/HEAD/plugins/testing-handbook-skills/skills/harness-writing

### Antigravity

In Antigravity: Copy the harness-writing folder into ~/.gemini/config/skills (Antigravity app and IDE) or ~/.gemini/antigravity-cli/skills (Antigravity CLI).

View the folder on GitHub: https://github.com/trailofbits/skills/tree/HEAD/plugins/testing-handbook-skills/skills/harness-writing

### Gemini CLI

Run in your terminal:

```shell
npx -y degit trailofbits/skills/plugins/testing-handbook-skills/skills/harness-writing ~/.gemini/skills/harness-writing
```

View the folder on GitHub: https://github.com/trailofbits/skills/tree/HEAD/plugins/testing-handbook-skills/skills/harness-writing

### Replit

Run in your terminal:

```shell
npx -y degit trailofbits/skills/plugins/testing-handbook-skills/skills/harness-writing .agents/skills/harness-writing
```

View the folder on GitHub: https://github.com/trailofbits/skills/tree/HEAD/plugins/testing-handbook-skills/skills/harness-writing

### OpenClaw

Run in your terminal:

```shell
npx -y degit trailofbits/skills/plugins/testing-handbook-skills/skills/harness-writing ~/.openclaw/skills/harness-writing
```

View the folder on GitHub: https://github.com/trailofbits/skills/tree/HEAD/plugins/testing-handbook-skills/skills/harness-writing

### OpenCode

Run in your terminal:

```shell
npx -y degit trailofbits/skills/plugins/testing-handbook-skills/skills/harness-writing ~/.config/opencode/skills/harness-writing
```

View the folder on GitHub: https://github.com/trailofbits/skills/tree/HEAD/plugins/testing-handbook-skills/skills/harness-writing

### Hermes Agent

Run in your terminal:

```shell
npx -y degit trailofbits/skills/plugins/testing-handbook-skills/skills/harness-writing ~/.hermes/skills/harness-writing
```

View the folder on GitHub: https://github.com/trailofbits/skills/tree/HEAD/plugins/testing-handbook-skills/skills/harness-writing

---
From Pluginboard (https://pluginboard.ai).