isolated-mongodb-integration-tests.md

Isolated MongoDB integration tests

Translations: Français

How to run disposable MongoDB databases in your AVA tests with per-test isolation.

This uses MongoMem, which allows you to quickly run a temporary MongoDB server locally. It uses temporary file storage which is destroyed when the server stops.

Install MongoDB in-memory Server (MongoMem)

In the root directory of your app, run:

$ npm install --save-dev mongomem

Using MongoMem

In your test file, import the module, and run the server.

Make sure to run the server at the start of your file, outside of any test cases.

import test from 'ava';
import {MongoDBServer} from 'mongomem';

test.before('start server', async t => {
	await MongoDBServer.start();
})

test('some feature', async t => {
	const connectionString = await MongoDBServer.getConnectionString();

	// connectionString === 'mongodb://localhost:27017/3411fd12-b5d6-4860-854c-5bbdb011cb93'
	// Use `connectionString` to connect to the database with a client of your choice. See below for usage with Mongoose.
});

Cleaning Up

After you have run your tests, you should include a test.after.always() method to clean up the MongoDB server. This will remove any temporary files the server used while running.

This is normally cleaned up by your operating system, but it is good practise to do it manually.

test.after.always('cleanup', t => {
	MongoDBServer.tearDown(); // Cleans up temporary file storage
});

Debugging

If the server does not seem to start, you can set the MongoDBServer.debug = true; option before you call MongoDBServer.start(). This will allow the MongoDB server to print connection or file permission errors when it's starting. It checks and picks an available port to run the server on, so errors are likely to be related to file permissions.

Extra: Setup and use in Mongoose (MongoDB ODM)

Mongoose is a robust Object-Document-Mapper (ODM) for MongoDB. Refer to its documentation to get started with Mongoose.

Import Mongoose

// `myTestCase.test.js` - (Your test case file)
import mongoose from 'mongoose';

mongoose in this case is a single instance of the Mongoose ODM and is globally available. This is great for your app as it maintains a single access point to your database, but less great for isolated testing.

You should isolate Mongoose instances between your tests, so that the order of test execution is never depended on. This can be done with a little bit of work.

Isolate Mongoose Instance

You can easily request a new instance of Mongoose. First, call new mongoose.Mongoose() to get the new instance, and then call connect with a database connection string provided by the mongomem package.

You will have to manually copy models from the global instance to your new instance.

import mongoose from 'mongoose';
import {MongoDBServer} from 'mongomem';

test.before('start server', async t => {
	await MongoDBServer.start();
});

test.beforeEach(async t => {
	const db = new mongoose.Mongoose();
	await db.connect(await MongoDBServer.getConnectionString());

	for (const name of mongoose.modelNames()) {
		db.model(name, mongoose.model(name).schema);
	}

	t.context.db = db;
});

test('my Mongoose model integration test', async t => {
	const {db} = t.context;
	// Now use the isolated DB instance in your test
});