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Agent skill

Coverage Drop Investigator

by proffesor-for-testing in proffesor-for-testing/agentic-qe

A skill your agent uses when test coverage has dropped and you need to find which changes caused it and what tests to add.

MITAuto-check passedTesting & QA

Install Coverage Drop Investigator

skills CLI
$ npx skills add proffesor-for-testing/agentic-qe --skill coverage-drop-investigator -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install proffesor-for-testing/agentic-qe coverage-drop-investigator --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/proffesor-for-testing/agentic-qe.git skills-src && mkdir -p .claude/skills && cp -r skills-src/assets/skills/coverage-drop-investigator .claude/skills/coverage-drop-investigator && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
coverage-drop-investigator
GitHub stars
495
Token cost
~761 tokens
SKILL.md length
159 words
Files
1
Skills in repo
93
Repo updated
First seen
Licence
MIT

At a glance

A skill your agent uses when test coverage has dropped and you need to find which changes caused it and what tests to add.

  • Works in 6 steps: Measure Current Coverage → Find When Coverage Dropped → Identify Uncovered Files → …
  • Test coverage has dropped and you need to find which changes caused it and what tests to add
  • SKILL.md covers Activation, Investigation Flow, Composition and Gotchas
  • Calls jq, npx and git

What it does

Coverage Drop Investigator is an agent skill from proffesor-for-testing/agentic-qe. Use when test coverage has dropped and you need to find which changes caused it and what tests to add. Traces coverage regressions to specific commits and files.

Its SKILL.md is about 760 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Testing & QA, covering Test coverage. The repository describes itself as: Agentic QE Fleet is an open-source AI-powered QA/QE platform designed for use with Coding Agents (works best with Claude Code) featuring specialized agents and skills to support… The licence is MIT.

When your agent uses it

  • Test coverage has dropped and you need to find which changes caused it and what tests to add
  • Tasks that involve Test coverage

Example prompts

  • “/coverage-drop-investigator”

Requirements

  • Node.js

Workflow steps

6 steps, taken from the step headings in SKILL.md.

  1. Measure Current Coverage
  2. Find When Coverage Dropped
  3. Identify Uncovered Files
  4. Map to Recent Changes
  5. Recommend Tests
  6. Report

What it can do on your machine

Read from SKILL.md and the folder at commit 1363bc7. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Shell commands in SKILL.md call:

    • jq
    • npx
    • git

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md. Its commands use npx and git, which can reach the network depending on how they are called.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Coverage Drop Investigator loads about 761 tokens when it runs. Until then it costs about 47 tokens; SKILL.md has 159 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~47
When it runs · the whole SKILL.md, loaded when a task matches
~761

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from proffesor-for-testing/agentic-qe at commit 1363bc7, republished under its MIT licence (© proffesor-for-testing). 159 words, ~761 tokens.

Download SKILL.mdSave it as .claude/skills/coverage-drop-investigator/SKILL.md (or your agent's skills folder).
name
coverage-drop-investigator
description
Use when test coverage has dropped and you need to find which changes caused it and what tests to add. Traces coverage regressions to specific commits and files.
user-invocable
true

Coverage Drop Investigator

Runbook-style skill for investigating coverage regressions. Identifies which changes caused coverage to drop and recommends targeted tests.

Activation

/coverage-drop-investigator

Investigation Flow

Step 1: Measure Current Coverage
bash
# Generate coverage report
npx jest --coverage --coverageReporters=json-summary

# View summary
cat coverage/coverage-summary.json | jq '.total'
Step 2: Find When Coverage Dropped
bash
# Compare coverage with main branch
git stash && npx jest --coverage --coverageReporters=json-summary
mv coverage/coverage-summary.json coverage/baseline.json
git stash pop && npx jest --coverage --coverageReporters=json-summary

# Compare
jq -s '.[0].total.statements.pct as $baseline | .[1].total.statements.pct as $current | {baseline: $baseline, current: $current, delta: ($current - $baseline)}' coverage/baseline.json coverage/coverage-summary.json
Step 3: Identify Uncovered Files
bash
# Find files with lowest coverage
cat coverage/coverage-summary.json | jq 'to_entries | map(select(.key != "total")) | sort_by(.value.statements.pct) | .[0:10] | .[] | {file: .key, statements: .value.statements.pct, branches: .value.branches.pct}'
Step 4: Map to Recent Changes
bash
# Find recently changed files with low coverage
git diff --name-only main...HEAD | while read file; do
  jq --arg f "$file" '.[$f] // empty | {file: $f, statements: .statements.pct}' coverage/coverage-summary.json
done
Step 5: Recommend Tests

For each uncovered file, identify:

  1. Uncovered functions — need new test cases
  2. Uncovered branches — need conditional test cases (if/else paths)
  3. Uncovered lines — may indicate dead code or missing edge cases
Step 6: Report
markdown
## Coverage Drop Report
- **Current**: {{current_pct}}%
- **Baseline (main)**: {{baseline_pct}}%
- **Delta**: {{delta}}%
- **Files causing drop**:
  | File | Coverage | Changed Lines | Tests Needed |
  |------|----------|--------------|-------------|
  | {{file}} | {{pct}}% | {{lines}} | {{count}} |
- **Recommended action**: {{write_tests / accept_drop / mark_as_excluded}}

Composition

After investigation:

  • /qe-test-generation — generate tests for uncovered files
  • /mutation-testing — verify existing tests actually catch bugs
  • /coverage-guard — prevent future drops

Gotchas

  • Coverage can drop because NEW code was added without tests, not because tests were removed
  • 100% coverage is not always the goal — focus on critical paths, not getters/setters
  • Branch coverage drops are more concerning than line coverage drops — branches indicate logic paths
  • Coverage tools may count generated code or type definitions — exclude with coveragePathIgnorePatterns

© proffesor-for-testing, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in assets/skills/coverage-drop-investigator of proffesor-for-testing/agentic-qe.

Open the folder on GitHubat commit 1363bc7

Compare with similar skills

Coverage Drop Investigator next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Coverage Drop Investigator compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Coverage Drop Investigator this skillproffesor-for-testing/agentic-qe495—~761Automated safety check: PassMIT
Requirementsrizsotto/Bear6.5k—~2kAutomated safety check: PassGPL-3.0
Crap Analysisardalis/RiverBooks1352 repos~3.4kAutomated safety check: PassNone
Bmad Testarch Automatechenjackle45/SayIt1152 repos~867Automated safety check: PassMIT
Code Coverages3s-project/s3s311—~789Automated safety check: PassApache-2.0
Project Statusbactopia/bactopia522—~787Automated safety check: PassMIT

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Categories

Questions about Coverage Drop Investigator

What does Coverage Drop Investigator do?

A skill your agent uses when test coverage has dropped and you need to find which changes caused it and what tests to add. Coverage Drop Investigator is an agent skill from proffesor-for-testing/agentic-qe. Use when test coverage has dropped and you need to find which changes caused it and what tests to add.

When should I use Coverage Drop Investigator?

Coverage Drop Investigator fits situations like: test coverage has dropped and you need to find which changes caused it and what tests to add; tasks that involve Test coverage.

How do I install Coverage Drop Investigator in Claude Code?

Run `npx skills add proffesor-for-testing/agentic-qe --skill coverage-drop-investigator -a claude-code`. Or copy the skill folder (assets/skills/coverage-drop-investigator in proffesor-for-testing/agentic-qe) into .claude/skills/coverage-drop-investigator in your project. Claude Code loads it when a task matches its description.

How do I install Coverage Drop Investigator in Codex?

Run `npx skills add proffesor-for-testing/agentic-qe --skill coverage-drop-investigator -a codex`. Or copy the skill folder (assets/skills/coverage-drop-investigator in proffesor-for-testing/agentic-qe) into .agents/skills/coverage-drop-investigator in your project. Codex loads it when a task matches its description.

Can I use Coverage Drop Investigator in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add proffesor-for-testing/agentic-qe --skill coverage-drop-investigator -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/coverage-drop-investigator, .gemini/skills/coverage-drop-investigator, .github/skills/coverage-drop-investigator and .opencode/skills/coverage-drop-investigator in your project.

What does Coverage Drop Investigator need to run?

Going by SKILL.md and its folder, Coverage Drop Investigator needs the command-line tools its instructions call (jq, npx and git). Our summary lists: Node.js.

Does Coverage Drop Investigator access the network?

SKILL.md contains no URLs. Its commands use npx and git, which can reach the network depending on how they are called. This is read from the text; nothing was executed.

Is Coverage Drop Investigator safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Coverage Drop Investigator use?

Coverage Drop Investigator is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Coverage Drop Investigator use?

About 761 tokens (SKILL.md is roughly 3k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Coverage Drop Investigator?

Skills that share tags, products or a category with Coverage Drop Investigator: Requirements (rizsotto/Bear, 6.5k stars), Crap Analysis (ardalis/RiverBooks, 135 stars), Bmad Testarch Automate (chenjackle45/SayIt, 115 stars) and Code Coverage (s3s-project/s3s, 311 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Coverage Drop Investigator?

proffesor-for-testing (a GitHub user) maintains it in proffesor-for-testing/agentic-qe, which has 495 GitHub stars. The repository holds 93 skills in this directory. The repository was last updated on October 9, 2026.

Source: proffesor-for-testing/agentic-qe on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.