coverage-analysis

coverage-analysis is a skill for Claude Code from marduk191/qwen3_mcp. It costs 23 tokens per session (4,989 once invoked), scanned A, a copy of coverage-analysis, MIT.

A way to measure which parts of a program are exercised during fuzzing. It shows whether fuzzing tests are reaching useful code paths and where input checks may be blocking progress.

In plain words
What is it for?
Use it to assess fuzzing harnesses, find unreachable code paths, investigate blocking conditions, and track fuzzing progress.
Why use it?
It helps determine whether a fuzzing setup is actually testing the intended code. Comparing coverage over time also shows whether changes to the test harness are improving reach.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: positional $N argument.

Part of the testing-handbook-skills plugin — 15 skills shipped together

Good fit Use it to assess fuzzing harnesses, find unreachable code paths, investigate blocking conditions, and track fuzzing progress.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/marduk191/qwen3_mcp/coverage-analysis
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 marduk191/qwen3_mcp --skill coverage-analysis
Clone the repo
git clone --depth 1 https://github.com/marduk191/qwen3_mcp

Made for: Claude Code.

Or install testing-handbook-skills, the plugin that ships this one along with the rest of its 15 skills.

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 coverage-analysis

README.md
[![agentmods](https://agentmods.dev/badge/skills/marduk191/qwen3_mcp/coverage-analysis/github.svg)](https://agentmods.dev/skills/marduk191/qwen3_mcp/coverage-analysis)
Your own site
<a href="https://agentmods.dev/skills/marduk191/qwen3_mcp/coverage-analysis"><img src="https://agentmods.dev/badge/skills/marduk191/qwen3_mcp/coverage-analysis/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 coverage-analysis

Your own site · 80×15
<a href="https://agentmods.dev/skills/marduk191/qwen3_mcp/coverage-analysis"><img src="https://agentmods.dev/badge/skills/marduk191/qwen3_mcp/coverage-analysis.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 23 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,989 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 97% copy Near-identical to another mod 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 $0.00023 $0.04989
Opus 5 $0.00012 $0.02495
Sonnet 5 $0.00005 $0.00998
Haiku 4.5 $0.00002 $0.00499

Measured 9d ago against content hash 9c98ce71f209, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

coverage-analysis 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 9d 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.

Origin

This is a copy

97% identical to coverage-analysis — 7 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

skills/testing-handbook-skills/skills/coverage-analysis/SKILL.md · 608 lines

How it starts

The opening of the file, as written. The whole thing — 608 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Coverage Analysis

Coverage analysis is essential for understanding which parts of your code are exercised during fuzzing. It helps identify fuzzing blockers like magic value checks and tracks the effectiveness of harness improvements over time.

Overview

Code coverage during fuzzing serves two critical purposes:

  1. Assessing harness effectiveness: Understand which parts of your application are actually executed by your fuzzing harnesses
  2. Tracking fuzzing progress: Monitor how coverage changes when updating harnesses, fuzzers, or the system under test (SUT)

Coverage is a proxy for fuzzer capability and performance. While coverage is not ideal for measuring fuzzer performance in absolute terms, it reliably indicates whether your harness works effectively in a given setup.

Key Concepts

Concept Description
Coverage instrumentation Compiler flags that track which code paths are executed
Corpus coverage Coverage achieved by running all test cases in a fuzzing corpus
Magic value checks Hard-to-discover conditional checks that block fuzzer progress
Coverage-guided fuzzing Fuzzing strategy that prioritizes inputs that discover new code paths
Coverage report Visual or textual representation of executed vs. unexecuted code

When to Apply

Apply this technique when:

  • Starting a new fuzzing campaign to establish a baseline
  • Fuzzer appears to plateau without finding new paths
  • After harness modifications to verify improvements
  • When migrating between different fuzzers
  • Identifying areas requiring dictionary entries or seed inputs
  • Debugging why certain code paths aren't reached

Skip this technique when:

  • Fuzzing campaign is actively finding crashes
  • Coverage infrastructure isn't set up yet
  • Working with extremely large codebases where full coverage reports are impractical
  • Fuzzer's internal coverage metrics are sufficient for your needs

Read the full file on GitHub · 608 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. 9d ago First seen · 608 lines · 23 tokens per session scan A 9c98ce71f209

Subscribe to this mod's changes

coverage-analysis is a skill published in the GitHub repository marduk191/qwen3_mcp (13 stars, last pushed 7mo ago), licensed MIT. It adds 23 tokens to every session and 4,989 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 97% identical to coverage-analysis, differing in 7 lines, and is treated as a copy.

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