MongoPrime

Description

A module for loading fixtures in Mongo for parallel testing using MongoDB prebuilt and loading data in memory using ephemeralForTest as the storage engine.

MongoPrime has support for parallel testing such as found in AVA. It achieves this by creating a proxy that listens to DB requests from your code and determines if the fixtures need to be loaded. A unique database is created for each test.

Installation

npm i mongoprime --save-dev

or:

yarn add mongoprime -D

Usage

In order for this to work you must create a random database name in your code for each test. The database host and port are avalable through the env variaables MONGO_PRIMER_DB_HOST and MONGO_PRIMER_DB_PORT if you load your code during the tests. Else they can be hardcoded (defaults to 127.0.0.1:27018 - can be changed in runtime options).

Example:

// yourcode.js
const uuid = require('uuid') // you can use any random method you prefer
const connection = `mongodb://${process.env.MONGO_PRIMER_DB_HOST}:${process.env.MONGO_PRIMER_DB_PORT}/${uuid()}`
// console.log(connection) // ex: mongodb://127.0.0.1:59971/f3abdd14-dce4-4b0c-8db1-5716177aa9b2

In your test, initialize the proxy in your before call (It will ensure it is loaded just once even when used with AVA which calls before for each test file).

// test.js
const { initProxy } = require('mongoprime')
const fixtures = require('./fixtures.js')
test.before(async (t) => initProxy({ fixtures })

In some cases your code may be loaded using require and your "random" database name will be the same for each test. You can turn debug on to show a log and verify that you are seeing multiple databases being primed for all your tests:

DEBUG=mongoprime yarn test

Look for multiple entries such as:

mongoprime Priming 1169f9ef-7803-49f8-890c-5af0d4f78eba

If you find that your tests do not show different generated name you will need to find a way create and assign a unique database name for each test.

To acheve this ensure you are cleaning the require cache in your tests using modules such as import-fresh and potentially clear-module with clear.all() if you are using things like node-config to store your test URI.

Examples

// Some db fetching code - i.e. whatever.js
const uuid = require('uuid')
// Create a random URI
const uri = `mongodb://127.0.0.1:27018/${uuid()}`
// Connect to Mongo
....
// Cool function that fetchs amazing things from db using fixtures
const fetchSomething = async () => { 
  ...
}

// Test file - i.e. things.spec.js
const fresh = require('import-fresh')
test(async t => {
  const { fetchSomething } = fresh('../../lib/whatever')
  const things = await fetchSomething()
  t.is(things.length, 1)  
})

In some cases such as when using node-config which generates immutables, the db name may persist in which case you need to do a deep clear.

// Sample node-config file - i.e. testjs
const uuid = require('uuid')
module.exports = {
  db: {
    connection: `mongodb://127.0.0.1:27018/${uuid()}`
  }
}

// Test file - i.e. things.spec.js
const fresh = require('import-fresh')
const clear = require('clear-module')
test(async t => {
  clear.all('config')
  const { fetchSomething } = fresh('../../lib/whatever')
  const things = await fetchSomething()
  t.is(things.length, 1)  
})

Fixture format

Fixtures should in the form of:

const fixtures = {
    collectionName: [{ name: 'Entry 1'}, { name: 'Entry 2'}, ...]
}

Multiple collections can be provided at once:

const fixtures = {
    collection1: [{...}],
    collection2: [{...}],
    ...
}

You can use ObjectId to establish relationships:

// fixtures.js
const { ObjectId } = require('mongoprimer') 
const users = [{ 
    _id: ObjectId()
    name: 'Harry Potter'
}, { 
    _id: ObjectId(),
    name: 'Voldermort'
}]

const horcruxes = [{
    name: 'diadem'
    user: users[0]._id
}]

const fixtures = { users, horcruxes }

module.exports = fixtures

If you just want to clear your db between tests you can provide empty collections:

const fixtures = {
    collection1: [], // No fixtures provide so will just be cleared
    collection2: [{....}],
    ...
}

API

initProxy(options)

Options:

fixtures: {}, // Fixture collection
host: '127.0.0.1', // Proxy host
port: 27018, // Proxy port
ignore: ['system', 'admin', 'local'], // Collections to ignore
path: null // Path for mongo metadata - defaults to randomly generated systm tmp dir

generateURL()

Convenience method to create a new unique connection string using uuids.

Example

const uri = generateURL() 
// ex: mongodb://127.0.0.1:59971/3abdd14-dce4-4b0c-8db1-5716177aa9b2

ObjectID

Convenience function from Mongo to create/cast ObjectIDs in your fixtures.

Changelog

####2.0.0

• Upgrade to Mongodb 3.x