react-testing

A guide to testing React applications with Vitest, React Testing Library, MSW v2, and Playwright. It covers components, hooks, mocked APIs, and end-to-end tests that check complete user flows.

In plain words
What is it for?
Use it for React component and hook tests, API mocking, and browser-based end-to-end testing.
Why use it?
It helps structure tests for different parts of a React application without guessing which testing approach to use.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/mindcockpit-ai/cognitive-core/react-testing
Any agent
npx skills add mindcockpit-ai/cognitive-core --skill react-testing
Clone the repo
git clone --depth 1 https://github.com/mindcockpit-ai/cognitive-core

Made for: Claude Code, Codex.

Per session 40 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,068 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin unknown No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00040 $0.02068
Opus 5 $0.00020 $0.01034
Sonnet 5 $0.00008 $0.00414
Haiku 4.5 $0.00004 $0.00207

Measured 2d ago against content hash 0c297fc5e623, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

react-testing scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

language-packs/react/skills/react-testing/SKILL.md · 258 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 258 lines · 40 tokens per session scan A 0c297fc5e623

Subscribe to this mod's changes

react-testing is a skill published in the GitHub repository mindcockpit-ai/cognitive-core (11 stars, last pushed 2mo ago), with no licence file. It adds 40 tokens to every session and 2,068 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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