A test-generation workflow that reads source code and creates test suites for Python or TypeScript projects using pytest, Vitest, or Jest. It starts with tests that may fail, which is the red phase of test-driven development (TDD).

Use it to create tests for functions and modules, scaffold missing suites, or begin a TDD workflow.

It helps fill gaps when code has little or no automated test coverage and makes expected behavior explicit.

test-writer — Skill for Claude Code by hamzaPixl/pixl-ai

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 hamzaPixl/pixl-ai --skill test-writer

Clone the repo

git clone --depth 1 https://github.com/hamzaPixl/pixl-ai

Made for: Claude Code.

Or install pixl-crew, the plugin that ships this one along with the rest of its 93 skills, 14 agents, 6 hooks.

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/hamzapixl/pixl-ai/test-writer/github.svg)](https://agentmods.dev/skills/hamzapixl/pixl-ai/test-writer)

Your own site

<a href="https://agentmods.dev/skills/hamzapixl/pixl-ai/test-writer"><img src="https://agentmods.dev/badge/skills/hamzapixl/pixl-ai/test-writer/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/hamzapixl/pixl-ai/test-writer"><img src="https://agentmods.dev/badge/skills/hamzapixl/pixl-ai/test-writer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 63 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,653 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	$0.00063	$0.01653
Opus 5.5	$0.00025	$0.00661
Sonnet 5.5	$0.00013	$0.00331
Haiku 4.5	$0.00006	$0.00165

Measured 1mo ago against content hash 980f14c9d164, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

test-writer 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 1mo 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.

packages/crew/skills/test-writer/SKILL.md · 188 lines

How it starts

The opening of the file, as written. The whole thing — 188 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Setup

Read config.json in this skill directory (if it exists) to load user defaults:

framework — test framework to use; if null, auto-detect from project files
coverage_threshold — target coverage %; default 80
style — test style preference; default describe-it

If framework is null and auto-detection is ambiguous, use AskUserQuestion: "Which test framework does this project use? (vitest / jest / pytest)" Store the answer back to config.json for future invocations.

Overview

Generates comprehensive test suites from existing source code. Reads public function signatures, infers expected behavior from names, types, and usage patterns, and writes failing tests (TDD red phase). The tests execute but may not pass — that's intentional, as the developer then makes them green.

Step 0: Detect Project and Framework

Signal	Framework	Test location
`vitest.config.*` or `vitest` in package.json	vitest	`__tests__/` or `*.test.ts` colocated
`jest.config.*` or `jest` in package.json	jest	`__tests__/` or `*.test.ts` colocated
`pytest.ini`, `pyproject.toml` with `[tool.pytest]`, or `conftest.py`	pytest	`tests/` mirror
User specifies framework	Use specified	Follow project convention

Follow the project's existing test file placement convention. If no tests exist yet, use the framework's default layout.

Step 1: Scan Source Code

For the target file(s) or directory:

Identify public functions/methods — exported functions, class methods, API handlers
Read type signatures — parameter types, return types, generics
Read docstrings/comments — expected behavior hints
Find usage examples — how the function is called elsewhere in the codebase
Identify edge cases — nullable params, empty arrays, boundary values, error conditions

Skip: private helpers, generated code, framework glue, getters/setters without logic.

Step 2: Generate Test Plan

Before writing tests, output a plan:

Read the full file on GitHub · 188 lines

Files

What ships with it

1 file 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.

config.json 618 B

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.

1mo ago First seen · 188 lines · 63 tokens per session scan A 980f14c9d164

Subscribe to this mod's changes

test-writer is a skill published in the GitHub repository hamzaPixl/pixl-ai (2 stars, last pushed 6mo ago), licensed MIT. It adds 63 tokens to every session and 1,653 once invoked, about $0.0003 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 2026-09-03.

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