Agent skill

Testing Gaps

Run coverage, inspect results, and identify missing test scenarios for a given source file.

MITAuto-check passedTesting & QA

Install Testing Gaps

skills CLI

$ npx skills add JamieMason/syncpack --skill testing-gaps -a claude-code

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

GitHub CLI

$ gh skill install JamieMason/syncpack testing-gaps --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/JamieMason/syncpack.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.claude/skills/testing-gaps .claude/skills/testing-gaps && 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/

Paste into Claude Code

Install the "testing-gaps" agent skill from https://github.com/JamieMason/syncpack/tree/main/.claude/skills/testing-gaps into .claude/skills/testing-gaps/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "testing-gaps", then confirm the skill loads.

Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

$skill-installer

$skill-installer install https://github.com/JamieMason/syncpack/tree/main/.claude/skills/testing-gaps

Type this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.

skills CLI

$ npx skills add JamieMason/syncpack --skill testing-gaps -a codex

Project install goes to .agents/skills/; add -g for ~/.codex/skills/.

GitHub CLI

$ gh skill install JamieMason/syncpack testing-gaps --agent codex

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/JamieMason/syncpack.git skills-src && mkdir -p .agents/skills && cp -r skills-src/.claude/skills/testing-gaps .agents/skills/testing-gaps && rm -rf skills-src

Use ~/.agents/skills/ instead of .agents/skills for a personal install.

Codex skills documentation · loads skills from .agents/skills/

Paste into Codex

Install the "testing-gaps" agent skill from https://github.com/JamieMason/syncpack/tree/main/.claude/skills/testing-gaps into .agents/skills/testing-gaps/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "testing-gaps", then confirm the skill loads.

Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add JamieMason/syncpack --skill testing-gaps -a cursor

Project install goes to .agents/skills/; add -g for ~/.cursor/skills/.

GitHub CLI

$ gh skill install JamieMason/syncpack testing-gaps --agent cursor

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/JamieMason/syncpack.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/.claude/skills/testing-gaps .cursor/skills/testing-gaps && rm -rf skills-src

Use ~/.cursor/skills/ instead of .cursor/skills for a personal install.

Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/

Paste into Cursor

Install the "testing-gaps" agent skill from https://github.com/JamieMason/syncpack/tree/main/.claude/skills/testing-gaps into .cursor/skills/testing-gaps/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "testing-gaps", then confirm the skill loads.

Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

gemini skills install

$ gemini skills install https://github.com/JamieMason/syncpack.git --path .claude/skills/testing-gaps

--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.

skills CLI

$ npx skills add JamieMason/syncpack --skill testing-gaps -a gemini-cli

Project install goes to .agents/skills/; add -g for ~/.gemini/skills/.

GitHub CLI

$ gh skill install JamieMason/syncpack testing-gaps --agent gemini-cli

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/JamieMason/syncpack.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/.claude/skills/testing-gaps .gemini/skills/testing-gaps && rm -rf skills-src

Use ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.

Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/

Paste into Gemini CLI

Install the "testing-gaps" agent skill from https://github.com/JamieMason/syncpack/tree/main/.claude/skills/testing-gaps into .gemini/skills/testing-gaps/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "testing-gaps", then confirm the skill loads.

Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

GitHub CLI

$ gh skill install JamieMason/syncpack testing-gaps

Installs for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).

skills CLI

$ npx skills add JamieMason/syncpack --skill testing-gaps -a github-copilot

Project install goes to .agents/skills/; add -g for ~/.copilot/skills/.

Manual copy

$ git clone --depth 1 https://github.com/JamieMason/syncpack.git skills-src && mkdir -p .github/skills && cp -r skills-src/.claude/skills/testing-gaps .github/skills/testing-gaps && rm -rf skills-src

Use ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.

GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/

Paste into GitHub Copilot

Install the "testing-gaps" agent skill from https://github.com/JamieMason/syncpack/tree/main/.claude/skills/testing-gaps into .github/skills/testing-gaps/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "testing-gaps", then confirm the skill loads.

GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add JamieMason/syncpack --skill testing-gaps -a opencode

OpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.

GitHub CLI

$ gh skill install JamieMason/syncpack testing-gaps --agent opencode

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/JamieMason/syncpack.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/.claude/skills/testing-gaps .opencode/skills/testing-gaps && rm -rf skills-src

Use ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.

OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/

Paste into OpenCode

Install the "testing-gaps" agent skill from https://github.com/JamieMason/syncpack/tree/main/.claude/skills/testing-gaps into .opencode/skills/testing-gaps/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "testing-gaps", then confirm the skill loads.

OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

Facts

Skill name: testing-gaps
GitHub stars: 2.1k
Token cost: ~766 tokens
SKILL.md length: 256 words
Files: 1
Skills in repo: 11
Repo updated: Sep 26, 2026
First seen: Oct 7, 2026
Licence: MIT

At a glance

Run coverage, inspect results, and identify missing test scenarios for a given source file.

Works in 5 steps: Run Coverage → Read Coverage Output → Classify Gaps → …
Analysing test coverage
SKILL.md covers Workflow, Step 1: Run Coverage, Step 2: Read Coverage Output and Step 3: Classify Gaps, plus 3 more sections
Calls cargo and just

What it does

Testing Gaps is an agent skill from JamieMason/syncpack. Run coverage, inspect results, and identify missing test scenarios for a given source file. Use when analysing test coverage or finding untested branches.

Its SKILL.md is about 770 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. It works with npm. The repository describes itself as: Consistent dependency versions in large JavaScript Monorepos. The licence is MIT.

When your agent uses it

Analysing test coverage
Finding untested branches

Example prompts

“/testing-gaps”

Workflow steps

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

Run Coverage
Read Coverage Output
Classify Gaps
Identify Missing Scenarios
Report

What it can do on your machine

Read from SKILL.md and the folder at commit 958d306. 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:
- cargo
- just
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
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

Testing Gaps loads about 766 tokens when it runs. Until then it costs about 42 tokens; SKILL.md has 256 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~42
When it runs · the whole SKILL.md, loaded when a task matches: ~766

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 JamieMason/syncpack at commit 958d306, republished under its MIT licence (© JamieMason). 256 words, ~766 tokens.

Download SKILL.mdSave it as .claude/skills/testing-gaps/SKILL.md (or your agent's skills folder).

name: testing-gaps
description: Run coverage, inspect results, and identify missing test scenarios for a given source file. Use when analysing test coverage or finding untested branches.

Testing Gaps

Find untested branches and missing real-world test scenarios for a source file.

Workflow

Run text coverage for the target file
Identify uncovered branches from the output
Cross-reference with test file to understand what's tested
Report uncovered branches + missing real-world scenarios

Step 1: Run Coverage

Use cargo llvm-cov with --text output (not --html) for parseable results.

bash

# Full coverage, filtered to target file
cargo llvm-cov test --text \
  --ignore-run-fail \
  --ignore-filename-regex '(_test.rs|\/test\/)' \
  2>/dev/null | sed -n '/TARGET_FILE\.rs:/,/^$/p'

Example for preferred_semver.rs:

bash

cargo llvm-cov test --text \
  --ignore-run-fail \
  --ignore-filename-regex '(_test.rs|\/test\/)' \
  2>/dev/null | sed -n '/preferred_semver\.rs:/,/^$/p'

Step 2: Read Coverage Output

The text format shows per-line execution counts:

  42|     80|        .and_then(|range| ...)     # Hit 80 times
  74|      0|        Some(preferred)            # Never hit
 321|      0|        instance.mark_conflict(...) # Never hit

count > 0 = covered
count = 0 = uncovered branch
^N annotations on sub-expressions show partial coverage within a line

Extract only uncovered lines

bash

... | grep -E '^\s+\d+\|\s+0\|'

Step 3: Classify Gaps

For each uncovered branch, determine:

What code path leads here? — Trace the if/else chain backward
What input would trigger it? — What package.json + config combination
Is it reachable? — Some branches may be defensive/unreachable
Is it worth testing? — Real-world scenario vs theoretical edge case

Category	Action
Real-world scenario never tested	Write a test
Edge case in existing logic	Write a test
Defensive branch (unreachable)	Note but skip
Dead code	Consider removing

Step 4: Identify Missing Scenarios

Beyond line coverage, look for missing combinations:

Feature A tested, Feature B tested, A+B never tested together
Only tested with one package, never with multiple
Only tested with highestSemver, never lowestSemver
Only tested with one range type (^), never others (>=, <=)
Only tested without semver groups, never with

Step 5: Report

Structure findings as:

Uncovered branches — Specific lines, what triggers them, why untested
Missing real-world scenarios — Combinations and interactions not covered

Running Tests After Adding Coverage

bash

just test                              # All tests
cargo test test_name -- --nocapture   # Specific test
just coverage                         # Regenerate coverage report

Files

Just SKILL.md in .claude/skills/testing-gaps of JamieMason/syncpack.

Open the folder on GitHubat commit 958d306

Compare with similar skills

Testing Gaps 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.

Testing Gaps compared with similar skills
Skill	Stars	Used in	Tokens	Auto-check	Licence	Repo updated
Testing Gaps this skillJamieMason/syncpack	2.1k	—	~766	Automated safety check: Pass	MIT	11 days ago
Django Verification Loopaffaan-m/ECC	274k	7 repos	~2.9k	Automated safety check: Pass	MIT	2 days ago
Write Testsryokun6/ryos	1.3k	—	~1.7k	Automated safety check: Pass	AGPL-3.0	today
Verify Docs TestsMichealWayne/fe-tools	207	—	~281	Automated safety check: Pass	None	29 days ago
Generate Testscoco-research/coco	473	—	~1.7k	Automated safety check: Pass	Custom licence	today
Activitypub TestingMicrock/ordinary-claude-skills	401	—	~712	Automated safety check: Pass	Custom licence	1 mo ago

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Questions about Testing Gaps

What does Testing Gaps do?

Run coverage, inspect results, and identify missing test scenarios for a given source file. Testing Gaps is an agent skill from JamieMason/syncpack. Run coverage, inspect results, and identify missing test scenarios for a given source file.

When should I use Testing Gaps?

Testing Gaps fits situations like: analysing test coverage; finding untested branches.

How do I install Testing Gaps in Claude Code?

Run `npx skills add JamieMason/syncpack --skill testing-gaps -a claude-code`. Or copy the skill folder (.claude/skills/testing-gaps in JamieMason/syncpack) into .claude/skills/testing-gaps in your project. Claude Code loads it when a task matches its description.

How do I install Testing Gaps in Codex?

Run `npx skills add JamieMason/syncpack --skill testing-gaps -a codex`. Or copy the skill folder (.claude/skills/testing-gaps in JamieMason/syncpack) into .agents/skills/testing-gaps in your project. Codex loads it when a task matches its description.

Can I use Testing Gaps 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 JamieMason/syncpack --skill testing-gaps -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/testing-gaps, .gemini/skills/testing-gaps, .github/skills/testing-gaps and .opencode/skills/testing-gaps in your project.

What does Testing Gaps need to run?

Going by SKILL.md and its folder, Testing Gaps needs the command-line tools its instructions call (cargo and just).

Does Testing Gaps access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Testing Gaps 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 Testing Gaps use?

Testing Gaps 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 Testing Gaps use?

About 766 tokens (SKILL.md is roughly 3.1k 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 Testing Gaps?

Skills that share tags, products or a category with Testing Gaps: Django Verification Loop (affaan-m/ECC, 274k stars), Write Tests (ryokun6/ryos, 1.3k stars), Verify Docs Tests (MichealWayne/fe-tools, 207 stars) and Generate Tests (coco-research/coco, 473 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Testing Gaps?

JamieMason (a GitHub user) maintains it in JamieMason/syncpack, which has 2,099 GitHub stars. The repository holds 11 skills in this directory. The repository was last updated on September 26, 2026.

Source: JamieMason/syncpack on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.

Install Testing Gaps

Facts

At a glance

What it does

When your agent uses it

Example prompts

Workflow steps

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

Testing Gaps

Workflow

Step 1: Run Coverage

Step 2: Read Coverage Output

Extract only uncovered lines

Step 3: Classify Gaps

Categories

Step 4: Identify Missing Scenarios

Step 5: Report

Running Tests After Adding Coverage

Files

Compare with similar skills

Similar skills

More from JamieMason/syncpack

Related

Questions about Testing Gaps