Generating Test Data

What it does

When your agent uses it

• Creating realistic fixtures
• Edge case test data
• With phrases like generate test data
• Create fixtures

Example prompts

• “generate test data”
• “create fixtures”
• “setup test database”
• “/generating-test-data”

Requirements

• Python 3
• Compatibility (from SKILL.md): Designed for Claude Code
• Pre-approved tools (allowed-tools): Read, Write, Edit, Grep, Glob, Bash(test:data-*)

Workflow steps

7 steps, taken from the first numbered list in SKILL.md.

1. 1Read the project's data models, TypeScript interfaces, database schemas, or ORM definitions to understand the shape of all entities.
2. 2For each entity, create a factory function that produces a valid default instance
3. 3Generate edge case data variants for each entity
4. 4Create relationship factories that build connected entity graphs
5. 5Generate database seed files for integration tests
6. 6Write fixture files in JSON, YAML, or TypeScript for static test data
7. 7Validate generated data against the schema to ensure factories remain in sync with model changes.

What it can do on your machine

Read from SKILL.md and the folder at commit 23ea8d4. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves these tools, so the agent can use them without asking each time:

  • Read
  • Write
  • Edit
  • Grep
  • Glob
  • Bash(test:data-*)

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Ships 2 files in scripts/ (Python), which the agent can run.

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  Links to these hosts (documentation or services it may open):

  • fakerjs.dev
  • github.com
  • factoryboy.readthedocs.io
  • chancejs.com
  • martinfowler.com

  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.

• Compatibility

  Designed for Claude Code

  From compatibility in the SKILL.md frontmatter.

Context cost

Generating Test Data loads about 1.5k tokens when it runs, and up to ~1.5k if it reads all its reference files. Until then it costs about 62 tokens; SKILL.md has 503 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~62

When it runs · the whole SKILL.md, loaded when a task matches

~1.5k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~1.5k

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

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); the scripts in this folder are not scanned.

SKILL.md

The full file from jeremylongshore/tons-of-skills-marketplace at commit 23ea8d4, republished under its MIT licence (© jeremylongshore). 503 words, ~1,523 tokens.

name

generating-test-data

description

Generate realistic test data including edge cases and boundary conditions. Use when creating realistic fixtures or edge case test data. Trigger with phrases like "generate test data", "create fixtures", or "setup test database".

allowed-tools

Read, Write, Edit, Grep, Glob, Bash(test:data-*)

compatibility

Designed for Claude Code

version

1.24.0

author

Jeremy Longshore <jeremy@intentsolutions.io>

license

MIT

tags

testing, database, test-data

import { Factory } from 'fishery';
import { faker } from '@faker-js/faker';

interface User {
  id: string;
  name: string;
  email: string;
  role: 'admin' | 'user';
  createdAt: Date;
}

export const userFactory = Factory.define<User>(({ sequence }) => ({
  id: `user-${sequence}`,
  name: faker.person.fullName(),
  email: faker.internet.email(),
  role: 'user',
  createdAt: faker.date.past(),
}));

// Usage:
const user = userFactory.build();
const admin = userFactory.build({ role: 'admin' });
const users = userFactory.buildList(10);

import pytest
from faker import Faker

fake = Faker()
Faker.seed(42)

@pytest.fixture
def make_user():
    def _make_user(**overrides):
        defaults = {
            "name": fake.name(),
            "email": fake.email(),
            "age": fake.random_int(min=18, max=99),
        }
        return {**defaults, **overrides}
    return _make_user

def test_user_validation(make_user):
    user = make_user(age=17)
    assert validate_age(user) is False

export const edgeCases = {
  strings: ['', ' ', '\t\n', 'a'.repeat(10000), '<script>alert(1)</script>',  # 10000: 10 seconds in ms
            "Robert'); DROP TABLE users;--", '\u0000null\u0000byte'],
  numbers: [0, -0, -1, Number.MAX_SAFE_INTEGER, NaN, Infinity, -Infinity],
  dates: [new Date(0), new Date('2024-02-29'), new Date('9999-12-31')],  # 2024: 9999 = configured value
};

© jeremylongshore, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 4 other files (scripts, references, assets) in skills/.curated/generating-test-data of jeremylongshore/tons-of-skills-marketplace.

• SKILL.md
• assets/README.md
• references/README.md
• scripts/README.md
• scripts/generate_data.py

Open the folder on GitHubat commit 23ea8d4