jest.env.js

const NodeEnvironment = require('jest-environment-node');
const { MongoClient } = require('mongodb');

const user = 'mongo';
const password = 'mongo';
const database = 'synor';
const uri = `mongodb://${user}:${password}@127.0.0.1:27017`;

const sleep = async ms => new Promise(resolve => setTimeout(resolve, ms));

const connectToMongoDB = async () => {
  const client = await MongoClient.connect(uri, { poolSize: 1 });
  const db = client.db(database);
  return { client, db };
};

async function waitForMongoDB() {
  try {
    const { client, db } = await connectToMongoDB();

    await db
      .command({ usersInfo: { user, db: database } })
      .then(({ users }) => {
        const userExists = users.length;
        if (!userExists) {
          return db.addUser(user, password, {
            roles: [{ role: 'dbOwner', db: database }]
          });
        }
      });

    await client.close();
  } catch (_) {
    await sleep(1000);
    return waitForMongoDB();
  }
}

class SynorDatabaseMongoDBTestEnvironment extends NodeEnvironment {
  constructor(config, context) {
    super(config, context);
    this.docblockPragmas = context.docblockPragmas;
  }

  async setup() {
    await super.setup();
    await waitForMongoDB();
  }

  async teardown() {
    await super.teardown();
  }

  runScript(script) {
    return super.runScript(script);
  }
}

module.exports = SynorDatabaseMongoDBTestEnvironment;