# Test Data Generator > Creates test fixtures, mock data, and test scenarios for unit and integration tests. Use when setting up test data, creating mocks, or generating test fixtures. - Skill: `tomevault-io/test-data-generator` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/test-data-generator` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/test-data-generator/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Integrations & APIs - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/test-data-generator --- # Test Data Generator Generate test data, fixtures, and mocks for testing. ## Quick Start Create a simple fixture: ```javascript const mockUser = { id: 1, name: 'Test User', email: 'test@example.com' } ``` ## Instructions ### Factory Functions Create reusable data generators: ```javascript function createUser(overrides = {}) { return { id: Math.floor(Math.random() * 1000), name: 'Test User', email: 'test@example.com', role: 'user', createdAt: new Date().toISOString(), ...overrides } } // Usage const admin = createUser({ role: 'admin', name: 'Admin User' }) const regularUser = createUser() ``` ```python def create_user(**kwargs): defaults = { 'id': random.randint(1, 1000), 'name': 'Test User', 'email': 'test@example.com', 'role': 'user', 'created_at': datetime.now() } return {**defaults, **kwargs} # Usage admin = create_user(role='admin', name='Admin User') ``` ### Builder Pattern For complex objects: ```javascript class UserBuilder { constructor() { this.user = { id: 1, name: 'Test User', email: 'test@example.com', role: 'user', preferences: {} } } withId(id) { this.user.id = id return this } withName(name) { this.user.name = name return this } withRole(role) { this.user.role = role return this } withPreferences(preferences) { this.user.preferences = preferences return this } build() { return this.user } } // Usage const user = new UserBuilder() .withId(123) .withName('John Doe') .withRole('admin') .withPreferences({ theme: 'dark' }) .build() ``` ### Test Fixtures **JavaScript/TypeScript**: ```javascript // fixtures/users.js export const users = { admin: { id: 1, name: 'Admin User', email: 'admin@example.com', role: 'admin' }, regular: { id: 2, name: 'Regular User', email: 'user@example.com', role: 'user' } } // In tests import { users } from './fixtures/users' test('admin can delete posts', () => { expect(canDelete(users.admin)).toBe(true) }) ``` **Python (pytest)**: ```python # conftest.py import pytest @pytest.fixture def sample_user(): return { 'id': 1, 'name': 'Test User', 'email': 'test@example.com', 'role': 'user' } @pytest.fixture def admin_user(): return { 'id': 2, 'name': 'Admin User', 'email': 'admin@example.com', 'role': 'admin' } # In tests def test_user_permissions(sample_user, admin_user): assert can_delete(admin_user) assert not can_delete(sample_user) ``` ### Mock Data **API Responses**: ```javascript const mockApiResponse = { data: { users: [ { id: 1, name: 'Alice' }, { id: 2, name: 'Bob' } ] }, status: 200, statusText: 'OK' } // Mock fetch global.fetch = jest.fn(() => Promise.resolve({ json: () => Promise.resolve(mockApiResponse.data) }) ) ``` **Database Records**: ```python mock_db_records = [ {'id': 1, 'name': 'Product A', 'price': 10.99}, {'id': 2, 'name': 'Product B', 'price': 20.99}, {'id': 3, 'name': 'Product C', 'price': 15.99} ] @patch('app.database.query') def test_get_products(mock_query): mock_query.return_value = mock_db_records products = get_products() assert len(products) == 3 ``` ### Random Data Generation **Using faker (JavaScript)**: ```javascript import { faker } from '@faker-js/faker' function generateUser() { return { id: faker.string.uuid(), name: faker.person.fullName(), email: faker.internet.email(), avatar: faker.image.avatar(), address: { street: faker.location.streetAddress(), city: faker.location.city(), country: faker.location.country() } } } // Generate multiple users const users = Array.from({ length: 10 }, generateUser) ``` **Using Faker (Python)**: ```python from faker import Faker fake = Faker() def generate_user(): return { 'id': fake.uuid4(), 'name': fake.name(), 'email': fake.email(), 'phone': fake.phone_number(), 'address': { 'street': fake.street_address(), 'city': fake.city(), 'country': fake.country() } } # Generate multiple users users = [generate_user() for _ in range(10)] ``` ### Seeded Random Data For reproducible tests: ```javascript import { faker } from '@faker-js/faker' test('generates consistent data with seed', () => { faker.seed(123) const user1 = generateUser() faker.seed(123) const user2 = generateUser() expect(user1).toEqual(user2) }) ``` ```python from faker import Faker def test_consistent_data(): fake = Faker() Faker.seed(123) user1 = generate_user(fake) Faker.seed(123) user2 = generate_user(fake) assert user1 == user2 ``` ### Mock Functions **Jest**: ```javascript const mockCallback = jest.fn(x => x * 2) test('calls callback for each item', () => { const items = [1, 2, 3] items.forEach(mockCallback) expect(mockCallback).toHaveBeenCalledTimes(3) expect(mockCallback).toHaveBeenCalledWith(1) expect(mockCallback).toHaveBeenCalledWith(2) expect(mockCallback).toHaveBeenCalledWith(3) }) ``` **Python (unittest.mock)**: ```python from unittest.mock import Mock def test_callback(): mock_callback = Mock(return_value=42) result = process_data([1, 2, 3], mock_callback) assert mock_callback.call_count == 3 mock_callback.assert_called_with(3) ``` ### Time-based Data **Freeze time**: ```javascript import { jest } from '@jest/globals' test('creates timestamp', () => { const mockDate = new Date('2024-01-01T00:00:00Z') jest.useFakeTimers() jest.setSystemTime(mockDate) const record = createRecord() expect(record.createdAt).toBe('2024-01-01T00:00:00.000Z') jest.useRealTimers() }) ``` ```python from freezegun import freeze_time @freeze_time("2024-01-01 00:00:00") def test_timestamp(): record = create_record() assert record['created_at'] == datetime(2024, 1, 1, 0, 0, 0) ``` ## Common Patterns **Pattern: Array of test cases**: ```javascript const testCases = [ { input: 'hello', expected: 'HELLO' }, { input: 'world', expected: 'WORLD' }, { input: '', expected: '' } ] testCases.forEach(({ input, expected }) => { test(`converts "${input}" to "${expected}"`, () => { expect(toUpperCase(input)).toBe(expected) }) }) ``` **Pattern: Shared setup**: ```javascript describe('UserService', () => { let service let mockDb beforeEach(() => { mockDb = { query: jest.fn(), insert: jest.fn() } service = new UserService(mockDb) }) test('fetches users', async () => { mockDb.query.mockResolvedValue([{ id: 1 }]) const users = await service.getUsers() expect(users).toHaveLength(1) }) }) ``` **Pattern: Test data files**: ```javascript // testData/users.json [ { "id": 1, "name": "Alice", "email": "alice@example.com" }, { "id": 2, "name": "Bob", "email": "bob@example.com" } ] // In tests import users from './testData/users.json' test('processes user data', () => { const result = processUsers(users) expect(result).toHaveLength(2) }) ``` ## Advanced For complex scenarios: - Use factory libraries (factory-bot, fishery, rosie) - Generate GraphQL mock data - Create database seeders - Build test data pipelines --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/armanzeroeight) — claim your Tome and manage your conversions.