Mutation Testing

Organization

Amplicode

mutation-testing

Set up and run mutation testing with PIT (pitest) on a Gradle project, and read the mutation score. Use this skill whenever the user wants mutation testing added to a build, configured, run or re-run, wants a mutation score or a mutation report interpreted, asks why a particular mutant survived, or asks what should be excluded from mutation analysis, or wants something added to those exclusions — in any language, and whether or not the tool is named. Also use it when the task calls for it: checking test quality rather than coverage — a high JaCoCo number can hide tests that assert nothing.

Overview

Publisher	Amplicode
Repository	`spring-skills`
Skill name	`mutation-testing`
Stars	134
Forks	15
Bundled files	7
Links	Skill source Repository

Markdown instructions
A SKILL.md file the model loads on demand, so it only costs tokens when a request actually matches.
Works with any LLM
AI skills are plain Markdown, not provider-specific code, so this works with GPT, Claude, Gemini, Grok, or a local model.
7 bundled files
Scripts, templates, and references the model can read while it works. Files are read-only and never executed.
Open source
Published by Amplicode on GitHub. Read the source before you install it.

Installation

Install the Mutation Testing AI skill in TypingMind to use it with any LLM, or drop it into another agent that reads SKILL.md.

Install in TypingMind

TypingMind installs a skill straight from its GitHub folder — it reads SKILL.md, bundles the resource files, and stores the result locally.

Open the app and go to Plugins → Skills.
Choose "Install from GitHub".
Paste the skill folder URL below and confirm.
https://github.com/Amplicode/spring-skills/tree/main/skills/mutation-testing
Enable the skill in any chat where you want it available.

Plugins → Skills → Add skill → From GitHub URL, then paste the folder URL and press Continue.

Install in another agent

Any agent that reads the Agent Skills format can use this skill — copy the folder into that agent's skills directory.

Claude Code — .claude/skills

git clone --depth 1 https://github.com/Amplicode/spring-skills.git /tmp/spring-skills
mkdir -p .claude/skills
cp -r /tmp/spring-skills/skills/mutation-testing .claude/skills/mutation-testing

Restart Claude Code after copying so it picks up the new skill.

Use it in TypingMind

Enable Mutation Testing in any TypingMind chat and the model takes it from there. Its name and description sit in the system prompt, and the moment a request matches, the model loads the full instructions itself — you never invoke it by hand, and it costs no tokens until it is actually used.

The model loads Mutation Testing on its own as soon as a request matches it.

Works with any AI model

AI skills are plain Markdown instructions rather than provider-specific code, so Mutation Testing is not tied to the model it was written for. Install it once in TypingMind and use it with GPT-5, Claude, Gemini, Grok, DeepSeek, Mistral, Llama, or a local model you run yourself — all on your own API keys.

Loaded only when it is needed
The system prompt carries just the name and description. The instructions are fetched on the first matching request, so an idle skill costs nothing.
Switch models mid-chat
Because the skill is instructions rather than code, changing model does not break it — the next model reads the same SKILL.md.

Skill instructions

This is the SKILL.md content the model loads. Read it before installing — a skill is instructions your model will follow.

Mutation testing

Steps

Start by reading this skill's own pitest entry for THIS project (type: project) — the checks below are built on it. A missing entry is not an error; it means nothing has been recorded yet.

Then work through the steps in order. Each carries a check: when the check fires the step is already done — skip it and move on. Load a step's reference only if you actually run that step, so there is context left for the PIT output.

1. Configure PIT in the build

Skip if PIT is already configured. Two signals say so — stop at the first hit:

The entry describes a configuration for this project. That is enough: skip the step, and do not spend a command confirming what the entry just said.

No entry — then ask the build file:

bash
grep -n "info.solidsoft.pitest" build.gradle build.gradle.kts 2>/dev/null

Otherwise follow references/configuration.md, which applies the exclusions as part of the setup.

If step 3 then fails with Task 'pitest' not found, the entry was stale: say so, run this step after all, and continue.

2. Adjust what gets mutated

Skip if the request has nothing to do with the exclusions or targetClasses.

Otherwise follow references/add-exclusion.md. It answers a question as well as it applies a change — when the request is only a question, stop after judging the candidate and leave the build alone.

3. Run PIT and report the score

Skip if the user asked only to wire PIT into the build, or only for advice on what to exclude — then say a run is available and stop there.

Otherwise follow references/usage.md.

4. Record what was resolved

Skip if the entry already describes what the run actually used.

Otherwise write or update pitest in the shape references/configuration.md step 5 defines. This is what lets step 1 be skipped next time, so it is not optional bookkeeping — dropping it makes the next run pay for the version probing and compatibility checks all over again.

Bundled files

The model reads these on demand while the skill is loaded. They are exposed as readable files and are never executed.

Frequently asked questions

What does the Mutation Testing AI skill do?

Why use Mutation Testing on TypingMind?

Because you install it once and use it with any model. Mutation Testing is plain Markdown rather than provider-specific code, so the same skill runs on GPT-5, Claude, Gemini, Grok, or a local model — and you can switch model mid-chat without it breaking. TypingMind runs on your own API keys, so you pay providers directly instead of a per-seat subscription, and your skills and chats stay in your own storage.

How do I install Mutation Testing in TypingMind?

Open Plugins → Skills → Install from GitHub in TypingMind and paste https://github.com/Amplicode/spring-skills/tree/main/skills/mutation-testing. TypingMind reads its SKILL.md and bundles its files and installs it as a skill you can enable per chat.

Which AI models can use Mutation Testing?

Any model you connect in TypingMind. AI skills are plain Markdown instructions rather than provider-specific code, so GPT, Claude, Gemini, Grok, and local models can all load this skill when a request matches it.

How many AI models can I use with Mutation Testing?

As many as you like. As long as a model supports skills, you can use Mutation Testing with it — GPT, Claude, Gemini, Grok, DeepSeek, Mistral, Llama and more — all on TypingMind with your own API keys.

Is the Mutation Testing AI skill free?

It is published on GitHub by Amplicode. Check the repository for licensing terms. You only pay your own AI provider for the tokens you use.

What are AI skills?

An AI skill is a reusable instruction bundle that teaches an AI model how to do one specific task. It follows the open Agent Skills format: a SKILL.md file with a name and description, plus any scripts, templates or reference files the model may need. The model reads the instructions only when your request matches the skill, so an installed skill costs nothing until it is used.

How are AI skills different from plugins or MCP servers?

A plugin or MCP server gives a model new tools to call — code that runs somewhere and returns a result. An AI skill gives the model knowledge and process instead: how to approach a task, which steps to follow, what good output looks like. Skills are plain Markdown, so they need no server, no API key and no runtime, and they work with any model.

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Overview

Installation

Install in TypingMind

Install in another agent

Use it in TypingMind

Works with any AI model

Skill instructions

Mutation testing

Steps

1. Configure PIT in the build

2. Adjust what gets mutated

3. Run PIT and report the score

4. Record what was resolved

Bundled files

Frequently asked questions

Related AI Skills

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