Official agent skill

React19 Test Patterns

Provides before/after patterns for migrating test files to React 19 compatibility, including act() imports, Simulate removal, and StrictMode call count changes.

OfficialMITAuto-check passed

Install React19 Test Patterns

skills CLI

$ npx skills add github/awesome-copilot --skill react19-test-patterns -a claude-code

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

GitHub CLI

$ gh skill install github/awesome-copilot react19-test-patterns --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/github/awesome-copilot.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/react19-test-patterns .claude/skills/react19-test-patterns && 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 "react19-test-patterns" agent skill from https://github.com/github/awesome-copilot/tree/main/skills/react19-test-patterns into .claude/skills/react19-test-patterns/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "react19-test-patterns", 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/github/awesome-copilot/tree/main/skills/react19-test-patterns

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 github/awesome-copilot --skill react19-test-patterns -a codex

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

GitHub CLI

$ gh skill install github/awesome-copilot react19-test-patterns --agent codex

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

Manual copy

$ git clone --depth 1 https://github.com/github/awesome-copilot.git skills-src && mkdir -p .agents/skills && cp -r skills-src/skills/react19-test-patterns .agents/skills/react19-test-patterns && 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 "react19-test-patterns" agent skill from https://github.com/github/awesome-copilot/tree/main/skills/react19-test-patterns into .agents/skills/react19-test-patterns/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "react19-test-patterns", 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 github/awesome-copilot --skill react19-test-patterns -a cursor

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

GitHub CLI

$ gh skill install github/awesome-copilot react19-test-patterns --agent cursor

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

Manual copy

$ git clone --depth 1 https://github.com/github/awesome-copilot.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/skills/react19-test-patterns .cursor/skills/react19-test-patterns && 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 "react19-test-patterns" agent skill from https://github.com/github/awesome-copilot/tree/main/skills/react19-test-patterns into .cursor/skills/react19-test-patterns/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "react19-test-patterns", 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/github/awesome-copilot.git --path skills/react19-test-patterns

--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 github/awesome-copilot --skill react19-test-patterns -a gemini-cli

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

GitHub CLI

$ gh skill install github/awesome-copilot react19-test-patterns --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/github/awesome-copilot.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/skills/react19-test-patterns .gemini/skills/react19-test-patterns && 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 "react19-test-patterns" agent skill from https://github.com/github/awesome-copilot/tree/main/skills/react19-test-patterns into .gemini/skills/react19-test-patterns/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "react19-test-patterns", 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 github/awesome-copilot react19-test-patterns

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 github/awesome-copilot --skill react19-test-patterns -a github-copilot

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

Manual copy

$ git clone --depth 1 https://github.com/github/awesome-copilot.git skills-src && mkdir -p .github/skills && cp -r skills-src/skills/react19-test-patterns .github/skills/react19-test-patterns && 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 "react19-test-patterns" agent skill from https://github.com/github/awesome-copilot/tree/main/skills/react19-test-patterns into .github/skills/react19-test-patterns/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "react19-test-patterns", 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 github/awesome-copilot --skill react19-test-patterns -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 github/awesome-copilot react19-test-patterns --agent opencode

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

Manual copy

$ git clone --depth 1 https://github.com/github/awesome-copilot.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/skills/react19-test-patterns .opencode/skills/react19-test-patterns && 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 "react19-test-patterns" agent skill from https://github.com/github/awesome-copilot/tree/main/skills/react19-test-patterns into .opencode/skills/react19-test-patterns/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "react19-test-patterns", 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: react19-test-patterns
GitHub stars: 40k
Used in: 1 other repo
Token cost: ~791 tokens
SKILL.md length: 166 words
Files: 1
Skills in repo: 417
Repo updated: Oct 8, 2026
First seen: Oct 7, 2026
Licence: MIT

At a glance

Provides before/after patterns for migrating test files to React 19 compatibility, including act() imports, Simulate removal, and StrictMode call count changes.

Works in 4 steps: act() Import Fix → Simulate → fireEvent → react-dom/test-utils Full API Map → …
SKILL.md covers Priority Order, 1. act() Import Fix, 2. Simulate → fireEvent and 3. react-dom/test-utils Full…, plus 1 more section
Calls npm

What it does

React19 Test Patterns is an agent skill from github/awesome-copilot, published by the product's own GitHub organization. Provides before/after patterns for migrating test files to React 19 compatibility, including act() imports, Simulate removal, and StrictMode call count changes.

Its SKILL.md is about 790 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It works with React. The repository describes itself as: Community-contributed instructions, agents, skills, and configurations to help you make the most of GitHub Copilot. The licence is MIT.

Example prompts

“Use the react19-test-patterns skill to provide before/after patterns for migrating test files to React 19 compatibility, including act() imports…”
“/react19-test-patterns”

Workflow steps

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

act() Import Fix
Simulate → fireEvent
react-dom/test-utils Full API Map
StrictMode Call Count Fixes

What it can do on your machine

Read from SKILL.md and the folder at commit 7cce7cf. 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:
- npm
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md. Its commands use npm, 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

React19 Test Patterns loads about 791 tokens when it runs. Until then it costs about 46 tokens; SKILL.md has 166 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~46
When it runs · the whole SKILL.md, loaded when a task matches: ~791

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 github/awesome-copilot at commit 7cce7cf, republished under its MIT licence (© github). 166 words, ~791 tokens.

Download SKILL.mdSave it as .claude/skills/react19-test-patterns/SKILL.md (or your agent's skills folder).

name: react19-test-patterns
description: Provides before/after patterns for migrating test files to React 19 compatibility, including act() imports, Simulate removal, and StrictMode call count changes.

React 19 Test Migration Patterns

Reference for all test file migrations required by React 19.

Priority Order

Fix test files in this order; each layer depends on the previous:

act import fix first, it unblocks everything else
Simulate → fireEvent fix immediately after act
Full react-dom/test-utils cleanup remove remaining imports
StrictMode call counts measure actual, don't guess
Async act wrapping for remaining "not wrapped in act" warnings
Custom render helper verify once per codebase, not per test

1. act() Import Fix

jsx

// Before  REMOVED in React 19:
import { act } from 'react-dom/test-utils';

// After:
import { act } from 'react';

If mixed with other test-utils imports:

jsx

// Before:
import { act, Simulate, renderIntoDocument } from 'react-dom/test-utils';

// After  split the imports:
import { act } from 'react';
import { fireEvent, render } from '@testing-library/react'; // replaces Simulate + renderIntoDocument

2. Simulate → fireEvent

jsx

// Before  Simulate REMOVED in React 19:
import { Simulate } from 'react-dom/test-utils';
Simulate.click(element);
Simulate.change(input, { target: { value: 'hello' } });
Simulate.submit(form);
Simulate.keyDown(element, { key: 'Enter', keyCode: 13 });

// After:
import { fireEvent } from '@testing-library/react';
fireEvent.click(element);
fireEvent.change(input, { target: { value: 'hello' } });
fireEvent.submit(form);
fireEvent.keyDown(element, { key: 'Enter', keyCode: 13 });

3. react-dom/test-utils Full API Map

Old (react-dom/test-utils)	New location
`act`	`import { act } from 'react'`
`Simulate`	`fireEvent` from `@testing-library/react`
`renderIntoDocument`	`render` from `@testing-library/react`
`findRenderedDOMComponentWithTag`	`getByRole`, `getByTestId` from RTL
`findRenderedDOMComponentWithClass`	`getByRole` or `container.querySelector`
`scryRenderedDOMComponentsWithTag`	`getAllByRole` from RTL
`isElement`, `isCompositeComponent`	Remove not needed with RTL
`isDOMComponent`	Remove

4. StrictMode Call Count Fixes

React 19 StrictMode no longer double-invokes useEffect in development. Spy assertions counting effect calls must be updated.

Strategy always measure, never guess:

bash

# Run the failing test, read the actual count from the error:
npm test -- --watchAll=false --testPathPattern="[filename]" --forceExit 2>&1 | grep -E "Expected|Received"

jsx

// Before (React 18 StrictMode  effects ran twice):
expect(mockFn).toHaveBeenCalledTimes(2);  // 1 call × 2 (strict double-invoke)

// After (React 19 StrictMode  effects run once):
expect(mockFn).toHaveBeenCalledTimes(1);

jsx

// Render-phase calls (component body)  still double-invoked in React 19 StrictMode:
expect(renderSpy).toHaveBeenCalledTimes(2);  // stays at 2 for render body calls

Files

Just SKILL.md in skills/react19-test-patterns of github/awesome-copilot.

Open the folder on GitHubat commit 7cce7cf

Used in 1 other repository

We found 1 copy of this SKILL.md (exact, near-identical or edited) in other folders, from 1 other GitHub owner. This page covers the copy in github/awesome-copilot, which our catalogue first saw on October 7, 2026.

boshi-xixixi/TraeSkill.trae/Skills/.agents/skills/react19-test-patterns

Compare with similar skills

React19 Test Patterns 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.

React19 Test Patterns compared with similar skills
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Vercel Composition Patternssupabase/supabase	111k	59 repos	~726	Automated safety check: Pass	MIT	today
React Doctormakeplane/plane	61k	12 repos	~657	Automated safety check: Pass	AGPL-3.0	today
React Router Developmentremix-run/react-router	57k	1 repos	~1.5k	Automated safety check: Pass	MIT	yesterday
React UI State PatternsChrisWiles/claude-code-showcase	6.1k	8 repos	~1.6k	Automated safety check: Pass	None	9 mo ago

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Questions about React19 Test Patterns

What does React19 Test Patterns do?

Provides before/after patterns for migrating test files to React 19 compatibility, including act() imports, Simulate removal, and StrictMode call count changes. React19 Test Patterns is an agent skill from github/awesome-copilot, published by the product's own GitHub organization. Provides before/after patterns for migrating test files to React 19 compatibility, including act() imports, Simulate removal, and StrictMode call count changes.

How do I install React19 Test Patterns in Claude Code?

Run `npx skills add github/awesome-copilot --skill react19-test-patterns -a claude-code`. Or copy the skill folder (skills/react19-test-patterns in github/awesome-copilot) into .claude/skills/react19-test-patterns in your project. Claude Code loads it when a task matches its description.

How do I install React19 Test Patterns in Codex?

Run `npx skills add github/awesome-copilot --skill react19-test-patterns -a codex`. Or copy the skill folder (skills/react19-test-patterns in github/awesome-copilot) into .agents/skills/react19-test-patterns in your project. Codex loads it when a task matches its description.

Can I use React19 Test Patterns 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 github/awesome-copilot --skill react19-test-patterns -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/react19-test-patterns, .gemini/skills/react19-test-patterns, .github/skills/react19-test-patterns and .opencode/skills/react19-test-patterns in your project.

What does React19 Test Patterns need to run?

Going by SKILL.md and its folder, React19 Test Patterns needs the command-line tools its instructions call (npm).

Does React19 Test Patterns access the network?

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

Is React19 Test Patterns 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 React19 Test Patterns use?

React19 Test Patterns 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 React19 Test Patterns use?

About 791 tokens (SKILL.md is roughly 3.2k 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 React19 Test Patterns?

Skills that share tags, products or a category with React19 Test Patterns: Web Artifacts Builder (anthropics/skills, 180k stars), Vercel Composition Patterns (supabase/supabase, 111k stars), React Doctor (makeplane/plane, 61k stars) and React Router Development (remix-run/react-router, 57k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains React19 Test Patterns?

github (a GitHub organization, an official publisher) maintains it in github/awesome-copilot, which has 39,792 GitHub stars. The repository holds 417 skills in this directory. The repository was last updated on October 8, 2026.

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

React19 Test Patterns

Install React19 Test Patterns

Facts

At a glance

What it does

Example prompts

Workflow steps

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

React 19 Test Migration Patterns

Priority Order

1. act() Import Fix

2. Simulate → fireEvent

3. react-dom/test-utils Full API Map

4. StrictMode Call Count Fixes

Files

Used in 1 other repository

Compare with similar skills

Similar skills

Web Artifacts Builder

Vercel Composition Patterns

React Doctor

React Router Development

React UI State Patterns

Stitch to Remotion Walkthrough Videos

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Questions about React19 Test Patterns

Install React19 Test Patterns

Facts

At a glance

What it does

Example prompts

Workflow steps

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

React 19 Test Migration Patterns

Priority Order

1. act() Import Fix

2. Simulate → fireEvent

3. react-dom/test-utils Full API Map

4. StrictMode Call Count Fixes

Files

Used in 1 other repository

Compare with similar skills

Similar skills

More from github/awesome-copilot

Related

Questions about React19 Test Patterns