testing

A testing guide for TypeScript and React projects. It explains how to choose between unit tests, component or hook tests, and tests for exact serialized output.

In plain words
What is it for?
Use it to decide where a test belongs, write assertions and fixtures, test React components or hooks, and keep a fast Bun test suite organized.
Why use it?
It helps keep tests focused on user-visible behavior while avoiding slow or unnecessary browser tests. It also gives rules for readable tests, small fixtures, and useful coverage checks.

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/udecode/plate-playground-template/testing
Any agent
npx skills add udecode/plate-playground-template --skill testing
Clone the repo
git clone --depth 1 https://github.com/udecode/plate-playground-template

Made for: Claude Code, Codex.

Per session 5 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 345 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original 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 $0.00005 $0.00345
Opus 5 $0.00003 $0.00172
Sonnet 5 $0.00001 $0.00069
Haiku 4.5 $0.00001 $0.00034

Measured 2d ago against content hash 3afb99842911, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

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.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

  • testing — 100% identical, 0 lines differ
.agents/skills/testing/SKILL.md · 53 lines

What it actually says

Testing Goal

Keep tests in three buckets only:

  • Pure unit tests for deterministic logic.
  • Thin component or hook contract tests for real app behavior.
  • Golden input or output tests when serialized output is the contract.

Hard constraints:

  • Prefer Bun for the fast local loop.
  • Keep the default suite fast.
  • No browser or e2e coverage unless the app behavior truly needs it.
  • Coverage is a hotspot tool, not a vanity score.

Core Rules

  • Assert public behavior, not implementation detail.
  • Keep tests next to the code they cover with *.spec.ts[x].
  • Keep helpers local. Do not import one spec from another.
  • Prefer explicit assertions over snapshots.
  • Delete skipped, commented, or placeholder tests instead of babysitting them.

Seam Selection

  • Use plain function tests for pure logic.
  • Use rendered React tests for hooks, components, rerender behavior, and DOM behavior.
  • Use browser checks only when the contract is actually browser-specific.

Fixtures And Assertions

  • Keep fixtures small.
  • Use plain objects for simple state.
  • Use it.each for small behavior matrices.
  • In Bun + Testing Library, prefer render-returned queries over screen.
  • Use direct style-property assertions instead of toHaveStyle.
  • Use snapshots only when serialized output is the contract and inline assertions would be worse.

Quick Reference

  • Keep tests fast and local.
  • Start with the smallest seam that proves the behavior.
  • Prefer explicit assertions.
  • Browser checks are for real UI behavior, not lazy coverage.
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 · 53 lines · 5 tokens per session scan A 3afb99842911

Subscribe to this mod's changes

testing is a skill published in the GitHub repository udecode/plate-playground-template (240 stars, last pushed 13d ago), licensed MIT. It adds 5 tokens to every session and 345 once invoked, about $0.0000 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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