In-memory MongoDB for test?

Question

I am writing some integration and system tests for my NodeJS application using a MongoDB database. The test framework I use is Mocha and Supertest. Is it possible to setup Mongo

Answer 1

You can accomplish this using mongodb-memory-server. The package downloads a mongod binary to your home directory and instantiates a new memory-backed MondoDB instance as needed. For each test file you can spin up a new server which means you can run them all parallel.

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For readers using jest and the native mongodb driver, you may find this class useful:

const { MongoClient } = require('mongodb');
const { MongoMemoryServer } = require('mongodb-memory-server');

// Extend the default timeout so MongoDB binaries can download
jest.setTimeout(60000);

// List your collection names here
const COLLECTIONS = [];

class DBManager {
  constructor() {
    this.db = null;
    this.server = new MongoMemoryServer();
    this.connection = null;
  }

  async start() {
    const url = await this.server.getUri();
    this.connection = await MongoClient.connect(url, { useNewUrlParser: true });
    this.db = this.connection.db(await this.server.getDbName());
  }

  stop() {
    this.connection.close();
    return this.server.stop();
  }

  cleanup() {
    return Promise.all(COLLECTIONS.map(c => this.db.collection(c).remove({})));
  }
}

module.exports = DBManager;

Then in each test file you can do the following:

const dbman = new DBManager();

afterAll(() => dbman.stop());
beforeAll(() => dbman.start());
afterEach(() => dbman.cleanup());

I suspect this approach may be similar for other testing frameworks.