fixture-interface

A JavaScript test fixture library that provides a simple interface for managing test data lifecycle across different storage backends.

Summary

This library solves the common testing problem of setting up and cleaning up test data. It provides a consistent interface for provisioning test data before tests run and automatically cleaning it up afterward, preventing test pollution and ensuring reliable test execution across different data stores.

How it works

Core Purpose:

• Setup: Bulk insert test data before tests run using the provision() method
• Cleanup: Automatically remove all test data after tests complete using the cleanup() method
• Track: Keep track of data created during test execution using the addData() method

Key Benefits:

• Prevents test pollution by ensuring clean data state between tests
• Supports different data stores (memory, DynamoDB, etc.) through inheritance
• Uses deep cloning to prevent accidental data modification
• Promise-based for async operations

Installation

npm install fixture-interface

Module Support

This package supports both CommonJS and ESM (ES Modules). Node.js will automatically use the appropriate version based on your project setup.

TypeScript Support

This package includes TypeScript declaration files (.d.ts) for full type safety and IntelliSense support in TypeScript projects.

Example Usage

1. Create a base fixture for your data store

CommonJS:

// base-fixtures/memory.fx.js
const Fixture = require('fixture-interface');
const memoryStore = require('../data-store/memory');

class MemoryFixture extends Fixture {
  insert(item) {
    memoryStore[item.id] = item;
    return Promise.resolve();
  }

  remove(item) {
    delete memoryStore[item.id];
    return Promise.resolve();
  }
}

module.exports = MemoryFixture;

ESM:

// base-fixtures/memory.fx.js
import Fixture from 'fixture-interface';
import memoryStore from '../data-store/memory.js';

class MemoryFixture extends Fixture {
  insert(item) {
    memoryStore[item.id] = item;
    return Promise.resolve();
  }

  remove(item) {
    delete memoryStore[item.id];
    return Promise.resolve();
  }
}

export default MemoryFixture;

2. Create domain-specific fixtures

CommonJS:

// fixtures/car.fx.js
const MemoryFixture = require('../base-fixtures/memory.fx');

class CarFixture extends MemoryFixture {
  insert(item) {
    // Add domain-specific logic
    item.hash_key = `${item.year};${item.make};${item.model}`;
    return super.insert(item);
  }

  remove(item) {
    return super.remove({id: item.hash_key});
  }
}

module.exports = CarFixture;

ESM:

// fixtures/car.fx.js
import MemoryFixture from '../base-fixtures/memory.fx.js';

class CarFixture extends MemoryFixture {
  insert(item) {
    // Add domain-specific logic
    item.hash_key = `${item.year};${item.make};${item.model}`;
    return super.insert(item);
  }

  remove(item) {
    return super.remove({id: item.hash_key});
  }
}

export default CarFixture;

3. Use in your tests

CommonJS:

// test.spec.js
const CarFixture = require('./fixtures/car.fx');
const testData = require('./fixture-data/cars.json');

describe('Car tests', () => {
  let carFixture;

  beforeEach(async () => {
    carFixture = new CarFixture();
    await carFixture.provision(testData); // Sets up all test data
  });

  afterEach(async () => {
    await carFixture.cleanup(); // Removes all test data
  });

  it('should find cars by make', () => {
    // Your test logic here - data is already provisioned
  });
});

ESM:

// test.spec.js
import CarFixture from './fixtures/car.fx.js';
import { readFileSync } from 'fs';
import { fileURLToPath } from 'url';
import { dirname, join } from 'path';

const __filename = fileURLToPath(import.meta.url);
const __dirname = dirname(__filename);
const testData = JSON.parse(readFileSync(join(__dirname, './fixture-data/cars.json'), 'utf8'));

describe('Car tests', () => {
  let carFixture;

  beforeEach(async () => {
    carFixture = new CarFixture();
    await carFixture.provision(testData); // Sets up all test data
  });

  afterEach(async () => {
    await carFixture.cleanup(); // Removes all test data
  });

  it('should find cars by make', () => {
    // Your test logic here - data is already provisioned
  });
});

4. Test data format

// fixture-data/cars.json
[
  {
    "year": 2000,
    "make": "Pontiac", 
    "model": "Grand Prix",
    "reviews": [
      {
        "author": "Rick Sanchez",
        "rating": 5,
        "review": "Great car!"
      }
    ]
  }
]

The fixture will provision this data before each test and clean it up afterward, ensuring each test starts with a known data state.