A software-testing guide covering test-driven development (TDD), end-to-end browser tests, test quality, Vitest tests, agent testing, and completion checks. TDD means writing a failing test before the code, then making it pass and cleaning up the implementation.

Use it to write tests first, find flaky or brittle tests, run Vitest or Playwright tests, test agents, or verify that a task is complete.

It provides defined testing steps and checks, helping avoid weak tests, missed verification, and unclear completion claims.

testing — Skill for Claude Code by notque/vexjoy-agent

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.

Any agent

npx skills add notque/vexjoy-agent --skill testing

Clone the repo

git clone --depth 1 https://github.com/notque/vexjoy-agent

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/notque/vexjoy-agent/testing/github.svg)](https://agentmods.dev/skills/notque/vexjoy-agent/testing)

Your own site

<a href="https://agentmods.dev/skills/notque/vexjoy-agent/testing"><img src="https://agentmods.dev/badge/skills/notque/vexjoy-agent/testing/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/notque/vexjoy-agent/testing"><img src="https://agentmods.dev/badge/skills/notque/vexjoy-agent/testing.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 23 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 4,766 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

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.

Model	Per session	Once invoked
Fable 5.1	$0.00023	$0.04766
Opus 5.5	$0.00009	$0.01906
Sonnet 5.5	$0.00005	$0.00953
Haiku 4.5	$0.00002	$0.00477

Measured yesterday against content hash aae305d4d046, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, 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 yesterday.

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.

skills/process/testing/SKILL.md · 475 lines

How it starts

The opening of the file, as written. The whole thing — 475 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Testing

Seven modes. Match the request to one mode and follow its section. Read repository CLAUDE.md first -- project conventions override defaults here.

Mode Selection

Request matches	Go to
Write tests first, TDD, red-green-refactor	TDD
Flaky, brittle, test smell, over-mocking, slow tests	Pattern Quality
Audit or prune low-value, duplicate, or implementation-coupled tests	Test Audit
Test an agent, subagent testing, validate agent	Agent Testing
Run vitest, JavaScript/TypeScript tests	Vitest Runner
Playwright, E2E, end-to-end, browser test	E2E (Playwright)
Verify completion, final check, defense in depth	Verification

TDD

RED-GREEN-REFACTOR cycle with strict phase gates. Each feature gets its own cycle. Do not batch multiple features into one cycle.

Phase 1: RED -- Write a Failing Test

Write a test describing desired behavior before implementation exists. Use Arrange-Act-Assert, descriptive names, one concept per test. Run the test and show full output.

Every new or changed test, in any mode, must first pass the authoring gate in references/audit-test-value.md.

Gate -- proceed only when all true:

Test file created and saved
Test executed
Output shows FAILURE (not syntax/import error)
Failure indicates missing implementation

If test passes before implementation: assertions are too weak, or the feature already exists. If test fails for wrong reason (syntax, import, setup): fix those first, then re-run until it fails for the right reason.

Phase 2: GREEN -- Minimum Implementation

Write ONLY enough code to make the failing test pass. No extra features. Hardcoded values are acceptable initially. Run the test and the full suite; show complete output.

Gate -- proceed only when all true:

New test passes
Full suite executed
No other tests broken

Phase 3: REFACTOR

Improve code quality without changing behavior. Establish a green baseline, refactor incrementally, run tests after every step. Test behavior, not internals.

Read the full file on GitHub · 475 lines

Files

What ships with it

19 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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.

yesterday Changed · +5 lines aae305d4d046
17d ago Changed · +32 lines · +4 tokens per session fbe977598514
20d ago Changed · +364 lines 69f787cca711
26d ago Changed · -364 lines bcfc0b805363
27d ago First seen · 438 lines · 19 tokens per session scan A 3f8c82216c33

Subscribe to this mod's changes

testing is a skill published in the GitHub repository notque/vexjoy-agent (442 stars, last pushed today), licensed MIT. It adds 23 tokens to every session and 4,766 once invoked, about $0.0001 per session on Opus 5.5. 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 2026-09-20.

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