test-factory-patterns

Testing & Quality

This skill provides guidance for writing test factories in the Packmind codebase. It should be used when creating or updating factory functions in `**/test/*Factory.ts` files to ensure realistic test data with variety.

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Test Factory Patterns

Overview

Test factories create realistic test data with variety. Good factories generate multiple plausible instances and randomly select one, while allowing partial overrides. Poor factories return identical static data every time.

The Pattern

Good Factory Structure

A well-designed factory:

Defines an array of multiple realistic instances with meaningful, varied content
Uses randomIn() to select one instance randomly
Spreads partial overrides to allow customization

import { Factory, randomIn } from '@packmind/test-utils';
import { Entity, createEntityId } from '@packmind/types';
import { v4 as uuidv4 } from 'uuid';

export const entityFactory: Factory<Entity> = (entity?: Partial<Entity>) => {
  const entities: Entity[] = [
    {
      id: createEntityId(uuidv4()),
      name: 'Meaningful Name One',
      slug: 'meaningful-name-one',
      content: `Realistic content that represents actual usage...`,
      // ... other fields with realistic values
    },
    {
      id: createEntityId(uuidv4()),
      name: 'Different Meaningful Name',
      slug: 'different-meaningful-name',
      content: `Different realistic content...`,
      // ... other fields with different realistic values
    },
    // Add 3-5 varied instances
  ];

  return {
    ...randomIn(entities),
    ...entity,
  };
};

Bad Factory Structure (Avoid)

Avoid factories that return identical static data:

// BAD: Always returns the same data
export const entityFactory: Factory<Entity> = (entity?: Partial<Entity>) => {
  return {
    id: createEntityId(uuidv4()),
    name: 'Test Entity', // Static, meaningless
    content: 'test content', // Not realistic
    ...entity,
  };
};

Guidelines

Content Quality

Use realistic, domain-appropriate content (not "test", "foo", "bar")
Include variety that reflects actual usage patterns
Make names and slugs consistent with each other

Instance Count

Include 3-5 varied instances in the array
Each instance should represent a plausible real-world case

Required Imports

import { Factory, randomIn } from '@packmind/test-utils';

ID Generation

Always generate fresh UUIDs for IDs using createXxxId(uuidv4())
Never hardcode static UUIDs

Override Support

Always spread partial overrides last: ...entity
This allows tests to customize specific fields while keeping realistic defaults