---
name: test-data-generation
description: >
  Generate realistic, consistent test data using factories, fixtures, and fake
  data libraries. Use for test data, fixtures, mock data, faker, test builders,
  and seed data generation.
---

# Test Data Generation

## Table of Contents

- [Overview](#overview)
- [When to Use](#when-to-use)
- [Quick Start](#quick-start)
- [Reference Guides](#reference-guides)
- [Best Practices](#best-practices)

## Overview

Test data generation creates realistic, consistent, and maintainable test data for automated testing. Well-designed test data reduces test brittleness, improves readability, and makes it easier to create diverse test scenarios.

## When to Use

- Creating fixtures for integration tests
- Generating fake data for development databases
- Building test data with complex relationships
- Creating realistic user inputs for testing
- Seeding test databases
- Generating edge cases and boundary values
- Building reusable test data factories

## Quick Start

Minimal working example:

```javascript
// tests/factories/userFactory.js
const { faker } = require("@faker-js/faker");

class UserFactory {
  static build(overrides = {}) {
    return {
      id: faker.string.uuid(),
      email: faker.internet.email(),
      firstName: faker.person.firstName(),
      lastName: faker.person.lastName(),
      age: faker.number.int({ min: 18, max: 80 }),
      phone: faker.phone.number(),
      address: {
        street: faker.location.streetAddress(),
        city: faker.location.city(),
        state: faker.location.state(),
        zip: faker.location.zipCode(),
        country: "USA",
      },
      role: "user",
      isActive: true,
      createdAt: faker.date.past(),
      ...overrides,
    };
  }
// ... (see reference guides for full implementation)
```

## Reference Guides

Detailed implementations in the `references/` directory:

| Guide | Contents |
|---|---|
| [Factory Pattern for Test Data](references/factory-pattern-for-test-data.md) | Factory Pattern for Test Data |
| [Builder Pattern for Complex Objects](references/builder-pattern-for-complex-objects.md) | Builder Pattern for Complex Objects |
| [Fixtures for Integration Tests](references/fixtures-for-integration-tests.md) | Fixtures for Integration Tests |
| [Realistic Data Generation](references/realistic-data-generation.md) | Realistic Data Generation |

## Best Practices

### ✅ DO

- Use faker libraries for realistic data
- Create reusable factories for common objects
- Make factories flexible with overrides
- Generate unique values where needed (emails, IDs)
- Use builders for complex object construction
- Create fixtures for integration test setup
- Generate edge cases (empty strings, nulls, boundaries)
- Keep test data deterministic when possible

### ❌ DON'T

- Hardcode test data in multiple places
- Use production data in tests
- Generate truly random data for reproducible tests
- Create overly complex factory hierarchies
- Ignore data relationships and constraints
- Generate massive datasets for simple tests
- Forget to clean up generated data
- Use the same test data for all tests