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Official agent skill

Code Testing Extensions

by microsoft in microsoft/testfx

Provides file paths to language-specific extension files for the code-testing pipeline.

OfficialMITAuto-check passedTesting & QA

Install Code Testing Extensions

skills CLI
$ npx skills add microsoft/testfx --skill code-testing-extensions -a claude-code

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

GitHub CLI
$ gh skill install microsoft/testfx code-testing-extensions --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/microsoft/testfx.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agents/skills/code-testing-extensions .claude/skills/code-testing-extensions && 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
code-testing-extensions
GitHub stars
1k
Used in
2 other repos
Token cost
~930 tokens
SKILL.md length
324 words
Files
17
Skills in repo
44
Repo updated
First seen
Licence
MIT

At a glance

Provides file paths to language-specific extension files for the code-testing pipeline.

  • Tasks that involve Unit testing
  • SKILL.md covers Available Extension Files and Usage
  • Calls go and cargo

What it does

Code Testing Extensions is an agent skill from microsoft/testfx, published by the product's own GitHub organization. Provides file paths to language-specific extension files for the code-testing pipeline. Call this skill to discover available extension guidance files (e.g., dotnet.md for .NET, cpp.md for C++). Do not use directly — invoked by code-testing agents and skills that need language-specific references.

Its SKILL.md is about 930 tokens, which your agent loads only when the skill is triggered. The skill folder holds 17 other files (for example `extensions/cpp.md`, `extensions/dotnet-examples.md` and `extensions/dotnet.md`).

It sits in Testing & QA, covering Unit testing. It works with C++, .NET, TypeScript and Java. The repository describes itself as: This repository holds the source code of Microsoft.Testing.Platform (MTP), a lightweight alternative to VSTest, as well as MSTest adapter and framework. The licence is MIT.

When your agent uses it

  • Tasks that involve Unit testing

Example prompts

  • “Use the code-testing-extensions skill to provide file paths to language-specific extension files for the code-testing pipeline”
  • “/code-testing-extensions”

Requirements

  • Python 3

What it can do on your machine

Read from SKILL.md and the folder at commit 44b9dcc. 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:

    • go
    • cargo

    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

Code Testing Extensions loads about 930 tokens when it runs. Until then it costs about 81 tokens; SKILL.md has 324 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~81
When it runs · the whole SKILL.md, loaded when a task matches
~930

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 microsoft/testfx at commit 44b9dcc, republished under its MIT licence (© microsoft). 324 words, ~930 tokens.

Download SKILL.mdSave it as .claude/skills/code-testing-extensions/SKILL.md (or your agent's skills folder). This skill also uses 16 other files; get the full folder from GitHub.
name
code-testing-extensions
description
Provides file paths to language-specific extension files for the code-testing pipeline. Call this skill to discover available extension guidance files (e.g., dotnet.md for .NET, cpp.md for C++). Do not use directly — invoked by code-testing agents and skills that need language-specific references.
user-invocable
false
license
MIT

Code Testing Extensions

This skill provides access to language-specific guidance files used by the code-testing pipeline. Call this skill to get the file paths, then read the relevant file for your target language.

Available Extension Files

FileLanguageContents
extensions/dotnet.md.NET (C#/F#/VB)Build commands, test commands, project reference validation, common CS error codes, MSTest template
extensions/python.mdPythonFramework-adaptive test commands (pytest, custom runners), project layout detection, mocking guidelines, common errors
extensions/typescript.mdTypeScript/JavaScriptBuild/test commands (Jest/Vitest/Mocha), framework detection, mocking, TS-specific considerations
extensions/powershell.mdPowerShellTest commands (Pester v5), module import patterns, discovery/run pitfalls, mocking, common errors
extensions/cpp.mdC++Testing internals with friend declarations
extensions/go.mdGogo test commands, table-driven tests, integration vs unit layout, mocking via interfaces, common errors
extensions/java.mdJavaMaven/Gradle commands, JUnit 4/5 and TestNG detection, Mockito, Spring Boot slices, common errors
extensions/rust.mdRustcargo test commands, unit vs integration vs doc tests, features, async test harnesses, common errors
extensions/ruby.mdRubyRSpec and Minitest commands, Bundler usage, Rails specifics, mocking patterns, common errors
extensions/swift.mdSwiftSPM and Xcode test commands, XCTest vs Swift Testing, @testable import, async/throws tests, common errors
extensions/kotlin.mdKotlinGradle commands, JUnit/Kotest detection, MockK, coroutines test, KMP and Android specifics, common errors
extensions/dotnet-examples.md.NET (C#/F#/VB)Concrete pipeline examples: sample research output, plan, generated tests, fix cycles, final report
extensions/python-examples.mdPythonConcrete pipeline examples (pytest): research, plan, generated test file, fix cycles, final report
extensions/typescript-examples.mdTypeScript/JavaScriptConcrete pipeline examples (Vitest, applicable to Jest): research, plan, generated test file, fix cycles, final report
extensions/go-examples.mdGoConcrete pipeline examples (standard testing): research, plan, table-driven test file, fix cycles, final report
extensions/java-examples.mdJavaConcrete pipeline examples (JUnit 5 + Mockito on Maven): research, plan, generated test file, fix cycles, final report

Usage

Read the appropriate extension file for the target language before writing test code. When an <language>-examples.md file exists for the target language, read it alongside the base extension to see a concrete end-to-end pipeline walkthrough (research output, plan, generated tests, fix cycles, final report).

© microsoft, 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 16 other files in .agents/skills/code-testing-extensions of microsoft/testfx.

  • SKILL.md
  • extensions/cpp.md
  • extensions/dotnet-examples.md
  • extensions/dotnet.md
  • extensions/go-examples.md
  • extensions/go.md
  • extensions/java-examples.md
  • extensions/java.md
  • extensions/kotlin.md
  • extensions/powershell.md
  • extensions/python-examples.md
  • extensions/python.md
  • extensions/ruby.md
  • extensions/rust.md
  • extensions/swift.md
  • extensions/typescript-examples.md
  • extensions/typescript.md

Open the folder on GitHubat commit 44b9dcc

Used in 2 other repositories

We found 3 copies of this SKILL.md (exact, near-identical or edited) in other folders, from 2 other GitHub owners. This page covers the copy in microsoft/testfx, which our catalogue first saw on October 7, 2026.

Compare with similar skills

Code Testing Extensions 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.

Code Testing Extensions compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Code Testing Extensions this skillmicrosoft/testfx1k2 repos~930Automated safety check: PassMIT
Test Smell Detectiondotnet/skills5.6k1 repos~2.5kAutomated safety check: PassMIT
Grade Testsdotnet/skills5.6k1 repos~5.2kAutomated safety check: PassMIT
CodeQL Security Scantrailofbits/skills7.4k—~4.6kAutomated safety check: NotesCC-BY-SA-4.0
Find Untested Sourcesdotnet/skills5.6k1 repos~3.3kAutomated safety check: PassMIT
Common Testing Conventionsmacalbert/envilder138—~1.9kAutomated safety check: PassMIT

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Works with

Categories

Questions about Code Testing Extensions

What does Code Testing Extensions do?

Provides file paths to language-specific extension files for the code-testing pipeline. Code Testing Extensions is an agent skill from microsoft/testfx, published by the product's own GitHub organization. Provides file paths to language-specific extension files for the code-testing pipeline.

When should I use Code Testing Extensions?

Code Testing Extensions fits situations like: tasks that involve Unit testing.

How do I install Code Testing Extensions in Claude Code?

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

How do I install Code Testing Extensions in Codex?

Run `npx skills add microsoft/testfx --skill code-testing-extensions -a codex`. Or copy the skill folder (.agents/skills/code-testing-extensions in microsoft/testfx) into .agents/skills/code-testing-extensions in your project. Codex loads it when a task matches its description.

Can I use Code Testing Extensions 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 microsoft/testfx --skill code-testing-extensions -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/code-testing-extensions, .gemini/skills/code-testing-extensions, .github/skills/code-testing-extensions and .opencode/skills/code-testing-extensions in your project.

What does Code Testing Extensions need to run?

Going by SKILL.md and its folder, Code Testing Extensions needs the command-line tools its instructions call (go and cargo). Our summary lists: Python 3.

Does Code Testing Extensions 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 Code Testing Extensions 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 Code Testing Extensions use?

Code Testing Extensions is published under the MIT licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Code Testing Extensions use?

About 930 tokens (SKILL.md is roughly 3.7k 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 Code Testing Extensions?

Skills that share tags, products or a category with Code Testing Extensions: Test Smell Detection (dotnet/skills, 5.6k stars), Grade Tests (dotnet/skills, 5.6k stars), CodeQL Security Scan (trailofbits/skills, 7.4k stars) and Find Untested Sources (dotnet/skills, 5.6k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Code Testing Extensions?

microsoft (a GitHub organization, an official publisher) maintains it in microsoft/testfx, which has 1,047 GitHub stars. The repository holds 44 skills in this directory. The repository was last updated on October 7, 2026.

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