In-memory MongoDB Server. Ideal for testing.
Clone or download
Latest commit b08739f Oct 29, 2018


This package provides an in-memory MongoDB Server. Designed with testing in mind, the server will allow you to connect your favourite ODM or client library to the MongoDB Server and run integration tests isolated from each other.

How it works This project is not an alternative in-memory MongoDB implementation. This runs using mongodb-prebuilt, which uses a MongoDB binary from NPM and runs it with the ephemeralForTest storage engine.

Note about AVA Test Runner The package was designed to run one server instance (max) at a time. As such it runs one server instance per test file in AVA (as a result of AVA using forked processes). This has no negative consequences but it does mean that you should call MongoDBServer.start() only once, at the top of an imported file or test file. Calling it in a helper method may result in either unexpected behaviour or multiple servers running per test file.


The example below uses async/await from ES7. If you wish to use the same syntax, you should transpile your code using babel-preset-es2017. Alternatively, if you are already using ES6 then you can convert it to the appropriate Promise syntax.

Available on NPM using: npm install mongomem --save-dev or yarn add mongomem --dev

See here for usage examples:

// helpers.js
import mongoose from 'mongoose'
import { MongoDBServer } from 'mongomem'

// MongoDBServer.debug = true;
let serverHasStarted = MongoDBServer.start();

export default {
  async getMongooseMock() {
      const mongooseInstance = new mongoose.Mongoose();
      await serverHasStarted;
      // MongoDBServer.getConnectionString() returns a new UUID4 on every call.
      // This allows you to get a unique database whilst utilising one in-memory server.
      let db = await MongoDBServer.getConnectionString();
      await mongooseInstance.connect(db, {promiseLibrary: Promise});
      // Re-assign original mongose models to new Mongoose connection
      Object.keys(mongoose.models).forEach(name => {
        const model = mongoose.models[name];
        mongooseInstance.model(name, model.schema);
      return mongooseInstance;