Jest: avoid topology-destroyed error by waiting for index creation in `afterAll`

setup.js

import mongoose from 'mongoose';
import MongodbMemoryServer from 'mongodb-memory-server';
let mongoServer;

beforeAll(async () => {
  mongoServer = new MongodbMemoryServer();
  const mongoUri = await mongoServer.getConnectionString();
  await mongoose.connect(
    mongoUri,
    {useNewUrlParser: true},
  );
});

afterAll(async () => {
  // via https://stackoverflow.com/a/51455290/2747869
  // Wait until indexes are created or you'll frequently get topology-destroyed errors
  await Promise.all(
    mongoose.modelNames().map(model => mongoose.model(model).createIndexes()),
  );
  await mongoose.disconnect();
  mongoServer.stop();
});

export async function resetDatabase() {
  await mongoose.connection.db.dropDatabase();
}