Coverage Report
n0an/VivaDicta
Measure VivaDicta test code coverage from the terminal. An agent skill from n0an/VivaDicta.
EXPERIMENTAL — mutation testing with muter to measure whether tests actually assert anything: mutants that survive reveal assertion-free coverage.
Install Mutation Testing
$ npx skills add rshankras/claude-code-apple-skills --skill mutation-testing -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install rshankras/claude-code-apple-skills mutation-testing --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/rshankras/claude-code-apple-skills.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/testing/mutation-testing .claude/skills/mutation-testing && rm -rf skills-srcUse ~/.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/
Install the "mutation-testing" agent skill from https://github.com/rshankras/claude-code-apple-skills/tree/main/skills/testing/mutation-testing into .claude/skills/mutation-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "mutation-testing", 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 install https://github.com/rshankras/claude-code-apple-skills/tree/main/skills/testing/mutation-testingType 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.
$ npx skills add rshankras/claude-code-apple-skills --skill mutation-testing -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install rshankras/claude-code-apple-skills mutation-testing --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/rshankras/claude-code-apple-skills.git skills-src && mkdir -p .agents/skills && cp -r skills-src/skills/testing/mutation-testing .agents/skills/mutation-testing && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "mutation-testing" agent skill from https://github.com/rshankras/claude-code-apple-skills/tree/main/skills/testing/mutation-testing into .agents/skills/mutation-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "mutation-testing", 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.
$ npx skills add rshankras/claude-code-apple-skills --skill mutation-testing -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install rshankras/claude-code-apple-skills mutation-testing --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/rshankras/claude-code-apple-skills.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/skills/testing/mutation-testing .cursor/skills/mutation-testing && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "mutation-testing" agent skill from https://github.com/rshankras/claude-code-apple-skills/tree/main/skills/testing/mutation-testing into .cursor/skills/mutation-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "mutation-testing", 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 https://github.com/rshankras/claude-code-apple-skills.git --path skills/testing/mutation-testing--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add rshankras/claude-code-apple-skills --skill mutation-testing -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install rshankras/claude-code-apple-skills mutation-testing --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/rshankras/claude-code-apple-skills.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/skills/testing/mutation-testing .gemini/skills/mutation-testing && rm -rf skills-srcUse ~/.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/
Install the "mutation-testing" agent skill from https://github.com/rshankras/claude-code-apple-skills/tree/main/skills/testing/mutation-testing into .gemini/skills/mutation-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "mutation-testing", 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.
$ gh skill install rshankras/claude-code-apple-skills mutation-testingInstalls 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).
$ npx skills add rshankras/claude-code-apple-skills --skill mutation-testing -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/rshankras/claude-code-apple-skills.git skills-src && mkdir -p .github/skills && cp -r skills-src/skills/testing/mutation-testing .github/skills/mutation-testing && rm -rf skills-srcUse ~/.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/
Install the "mutation-testing" agent skill from https://github.com/rshankras/claude-code-apple-skills/tree/main/skills/testing/mutation-testing into .github/skills/mutation-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "mutation-testing", 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.
$ npx skills add rshankras/claude-code-apple-skills --skill mutation-testing -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install rshankras/claude-code-apple-skills mutation-testing --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/rshankras/claude-code-apple-skills.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/skills/testing/mutation-testing .opencode/skills/mutation-testing && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "mutation-testing" agent skill from https://github.com/rshankras/claude-code-apple-skills/tree/main/skills/testing/mutation-testing into .opencode/skills/mutation-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "mutation-testing", 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
mutation-testing- GitHub stars
- 783
- Token cost
- ~1.1k tokens
- SKILL.md length
- 518 words
- Files
- 2
- Skills in repo
- 41
- Repo updated
- First seen
- Licence
- MIT
At a glance
EXPERIMENTAL — mutation testing with muter to measure whether tests actually assert anything: mutants that survive reveal assertion-free coverage.
- Works in 3 steps: Install muter and confirm it runs… → Copy templates/muter.conf.yml to the… → First run
- Tasks that involve Test coverage
- SKILL.md covers When This Skill Activates, Setup, Scoping: Engines Only and Reading the Report, plus 4 more sections
- Calls brew
What it does
Mutation Testing is an agent skill from rshankras/claude-code-apple-skills. EXPERIMENTAL — mutation testing with muter to measure whether tests actually assert anything: mutants that survive reveal assertion-free coverage. Advisory report only, never a merge gate. Use on engine/logic targets when coverage numbers look good but bugs still slip through.
Its SKILL.md is about 1.1k tokens, which your agent loads only when the skill is triggered. The skill folder holds 2 other files (for example `templates/muter.conf.yml`).
It sits in Testing & QA, covering Test coverage. It works with Xcode. The repository describes itself as: Claude Code skills for Apple platform development (iOS, macOS, iPadOS) — product validation, code generation, App Store optimization, and more. The licence is MIT.
When your agent uses it
- Tasks that involve Test coverage
Example prompts
- “/mutation-testing”
Requirements
- Pre-approved tools (allowed-tools): Read, Write, Edit, Glob, Grep, Bash
Workflow steps
3 steps, taken from the first numbered list in SKILL.md.
- Install muter and confirm it runs against the current Xcode before investing further
- Copy templates/muter.conf.yml to the repo root as muter.conf.yml and scope it (see below).
- First run
What it can do on your machine
Read from SKILL.md and the folder at commit 9ffb831. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves these tools, so the agent can use them without asking each time:
ReadWriteEditGlobGrepBash
From allowed-tools in the SKILL.md frontmatter.
Runs code
Shell commands in SKILL.md call:
brew
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
Mutation Testing loads about 1.1k tokens when it runs. Until then it costs about 74 tokens; SKILL.md has 518 words of instructions outside code blocks.
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: notes
The automated check noted patterns worth knowing about, such as sudo or a known installer.
- NotePre-approves every shell command (allowed-tools: Bash)SKILL.md
allowed-tools: Read, Write, Edit, Glob, Grep, Bash
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 rshankras/claude-code-apple-skills at commit 9ffb831, republished under its MIT licence (© rshankras). 518 words, ~1,089 tokens.
Download SKILL.mdSave it as
.claude/skills/mutation-testing/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.- name
- mutation-testing
- description
- EXPERIMENTAL — mutation testing with muter to measure whether tests actually assert anything: mutants that survive reveal assertion-free coverage. Advisory report only, never a merge gate. Use on engine/logic targets when coverage numbers look good but bugs still slip through.
- allowed-tools
- Read, Write, Edit, Glob, Grep, Bash
- last_verified
- 2026-07-24
- review_by
- 2027-07-01
Mutation Testing (Experimental)
Status: EXPERIMENTAL — advisory report only. Never wire this as a merge gate.
Coverage proves a line ran under test; mutation testing proves a test would notice if the line were wrong. Muter mutates the source (flips > to <, && to ||, deletes statements), reruns the suite per mutant, and reports the mutants that survived — code that is covered but effectively unasserted. It is the truest answer to "did the agent write real tests or coverage theater," and also the slowest and most fragile tool in the gauntlet, which is why it stays advisory.
When This Skill Activates
Use this skill when:
- Coverage is healthy but bugs still slip through covered code
- Auditing agent-written test suites for assertion-free tests
- A periodic (nightly/weekly) quality audit of engine/logic targets
Do NOT use as a per-commit or merge-blocking check — a full mutation run multiplies the suite's runtime by the mutant count.
Setup
- Install muter and confirm it runs against the current Xcode before investing further:
brew install muter-mutation-testing/formulae/muter
muter --version- Copy
templates/muter.conf.ymlto the repo root asmuter.conf.ymland scope it (see below). - First run:
muter run # writes an HTML/console report of surviving mutantsScoping: Engines Only
Mutation-test the code where logic density is highest and the suite claims real coverage — engine/store/service types. Exclude UI, generated code, and test files: mutating a SwiftUI body mostly produces noise, and every excluded file cuts the runtime multiplier.
mutateSourcesInDirectories:
- App/Engines
- App/Stores
excludeList:
- "*View.swift"
- "*Preview*"Reading the Report
- Killed mutant — a test failed: the suite genuinely asserts this behavior.
- Survived mutant — every test passed with the code broken: coverage without verification. Each survivor is a concrete, located prompt: write the assertion that kills it.
- Mutation score (killed ÷ total) is a trend number for the same scope over time; do not chase an absolute score.
Show full SKILL.md (239 more words)Show less
Caveats (Why This Stays Advisory)
- Toolchain fragility: muter rewrites source and drives xcodebuild; new Xcode releases can break it until the project catches up. Always verify a plain
muter runcompletes on the current toolchain before trusting results. - Swift Testing detection: muter's kill detection matured on XCTest. Verify it detects Swift Testing (
#expect) failures in YOUR project: run one mutant cycle on a file whose suite you trust, and confirm survivors/kills match expectations. - Runtime: suite time × mutants. Scope hard, run nightly or on demand.
Deterministic Fallback: Manual Mutation Spot-Checks
When muter can't run (toolchain break, CI limits), the drill from testing/fitness-functions/ scales down to single mutations by hand:
- Pick a critical function; invert one condition (or return a constant).
- Run its suite — a test MUST fail. If nothing fails, the suite has an assertion gap: write the missing test now.
- Revert. Two or three spot-checks per engine per release is a meaningful audit.
Common Pitfalls
| Pitfall | Problem | Solution |
|---|---|---|
| Wiring as a merge gate | Runtime + fragility block everyone | Nightly/on-demand advisory report |
| Mutating the whole app | Hours of UI-noise mutants | Scope to engine/store directories |
| Chasing a score | Score varies with scope, not quality | Track survivors fixed, not the percentage |
| Trusting an unverified run | Kill detection may miss the test framework | Calibrate on a suite you trust first |
References
testing/coverage-ratchet/— the cheap proxy this tool auditstesting/fitness-functions/— deliberate-break drill (the manual fallback)testing/tdd-feature/— writing the assertions that kill survivors
© rshankras, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
SKILL.md and 1 other file in skills/testing/mutation-testing of rshankras/claude-code-apple-skills.
- SKILL.md
- templates/muter.conf.yml
Open the folder on GitHubat commit 9ffb831
Compare with similar skills
Mutation Testing 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.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Mutation Testing this skillrshankras/claude-code-apple-skills | 783 | — | ~1.1k | Automated safety check: Notes | MIT | |
| Coverage Reportn0an/VivaDicta | 131 | — | ~1.2k | Automated safety check: Pass | MIT | |
| Xcsiftldomaradzki/xcsift | 489 | — | ~1.2k | Automated safety check: Pass | MIT | |
| Test Writing WorkflowiOfficeAI/AionUi | 33k | 1 repos | ~1.2k | Automated safety check: Pass | Apache-2.0 | |
| Evaluate PR Testsdotnet/maui | 23k | — | ~2.9k | Automated safety check: Pass | MIT | |
| Integration Testtracewayapp/traceway | 1.6k | 1 repos | ~2.4k | Automated safety check: Pass | MIT |
Similar skills
Xcsift
ldomaradzki/xcsift
Use xcsift for all Swift and Xcode build commands. An agent skill from ldomaradzki/xcsift.
Test Writing Workflow
iOfficeAI/AionUi
Sets the test-writing workflow for the repository: risk-first scenario lists, behavior-focused Vitest tests, a full run before each commit and a coverage target.
- Official
Evaluate PR Tests
dotnet/maui
Reviews the tests added in a pull request for fix coverage, quality, edge cases and test type, and recommends lighter test types where they would do.
Integration Test
tracewayapp/traceway
Run a live-instance verification of traceway-cli that goes beyond the Go smoke suite — exercises real-data detail endpoints, TTY-default rendering, adaptive metric-name discovery, and emits a…
Requirements
rizsotto/Bear
Write, modify, or review a requirement file under docs/requirements -- pick the single owning file, keep the text contract-only, name IDs so they need no explanation, and verify cross-references and…
More from rshankras/claude-code-apple-skills
All 41 skills in this repoAccessibility Generator
rshankras/claude-code-apple-skills
Generate accessibility infrastructure for VoiceOver, Dynamic Type, and accessibility features.
Animation Patterns
rshankras/claude-code-apple-skills
SwiftUI animation patterns including springs, transitions, PhaseAnimator, KeyframeAnimator, SF Symbol effects, scroll-driven effects, mesh gradients, text renderers, and shader effects.
App Description Writer
rshankras/claude-code-apple-skills
Generate compelling App Store descriptions that convert browsers into users.
App Icon Generator
rshankras/claude-code-apple-skills
Generates an app icon for macOS or iOS — a fast CoreGraphics placeholder and/or flat layered source art to finish in Icon Composer (the Liquid Glass / iOS 26+ standard).
App Namer
rshankras/claude-code-apple-skills
Turn an app idea into validated, App-Store-ready name candidates.
Bundles And Licensing
rshankras/claude-code-apple-skills
Revenue beyond the single-app price tag — own-app bundles, Family Sharing as a conversion lever, cross-developer bundles & suites, and institutional licensing via Group Purchases / Apple School &…
Related
Works with
Categories
Questions about Mutation Testing
What does Mutation Testing do?
EXPERIMENTAL — mutation testing with muter to measure whether tests actually assert anything: mutants that survive reveal assertion-free coverage. Mutation Testing is an agent skill from rshankras/claude-code-apple-skills. EXPERIMENTAL — mutation testing with muter to measure whether tests actually assert anything: mutants that survive reveal assertion-free coverage.
When should I use Mutation Testing?
Mutation Testing fits situations like: tasks that involve Test coverage.
How do I install Mutation Testing in Claude Code?
Run `npx skills add rshankras/claude-code-apple-skills --skill mutation-testing -a claude-code`. Or copy the skill folder (skills/testing/mutation-testing in rshankras/claude-code-apple-skills) into .claude/skills/mutation-testing in your project. Claude Code loads it when a task matches its description.
How do I install Mutation Testing in Codex?
Run `npx skills add rshankras/claude-code-apple-skills --skill mutation-testing -a codex`. Or copy the skill folder (skills/testing/mutation-testing in rshankras/claude-code-apple-skills) into .agents/skills/mutation-testing in your project. Codex loads it when a task matches its description.
Can I use Mutation Testing 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 rshankras/claude-code-apple-skills --skill mutation-testing -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/mutation-testing, .gemini/skills/mutation-testing, .github/skills/mutation-testing and .opencode/skills/mutation-testing in your project.
What does Mutation Testing need to run?
Going by SKILL.md and its folder, Mutation Testing needs the command-line tools its instructions call (brew). Its frontmatter pre-approves these tools: Read, Write, Edit, Glob, Grep, Bash.
Does Mutation Testing 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 Mutation Testing safe to install?
Our automated static check of SKILL.md found notes only (pre-approves every shell command (allowed-tools: bash)), nothing it rates as a warning. It is not a guarantee. Review the folder before installing.
What licence does Mutation Testing use?
Mutation Testing 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 Mutation Testing use?
About 1.1k tokens (SKILL.md is roughly 4.4k 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 Mutation Testing?
Skills that share tags, products or a category with Mutation Testing: Coverage Report (n0an/VivaDicta, 131 stars), Xcsift (ldomaradzki/xcsift, 489 stars), Test Writing Workflow (iOfficeAI/AionUi, 33k stars) and Evaluate PR Tests (dotnet/maui, 23k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Mutation Testing?
rshankras (a GitHub user) maintains it in rshankras/claude-code-apple-skills, which has 783 GitHub stars. The repository holds 41 skills in this directory. The repository was last updated on July 24, 2026.
Source: rshankras/claude-code-apple-skills on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.