mock-req-res

Extensible mock req / res objects for use in unit tests of ExpressJS controller and middleware functions.

Prerequisites

This library assumes:

1. You are using NodeJS 8+
2. You write properly isolated unit tests of route controllers and ExpressJS middleware functions
3. You use sinon version 5 or better.

Install

Add mock-req-res as a devDependency:

npm i -D mock-req-res

If you are using TypeScript you can add @types/mock-req-res:

npm i -D @types/mock-req-res

Mocking req

To test a controller or middleware function you need to mock a request object.

Do this with:

const req = mockRequest(options)

The options can be anything you wish to attach or override in the request.

The vanilla mockRequest gives you the following properties, as well as functions in the form of sinon stubs.

app: {},
baseUrl: '',
body: {},
cookies: {},
fresh: true,
headers: {},
hostname: '',
ip: '127.0.0.1',
ips: [],
method: 'GET',
originalUrl: '',
params: {},
path: '',
protocol: 'https',
query: {},
route: {},
secure: true,
signedCookies: {},
stale: false,
subdomains: [],
xhr: true,
accepts: stub(),
acceptsCharsets: stub(),
acceptsEncodings: stub(),
acceptsLanguages: stub(),
get: stub(),
is: stub(),
range: stub(),

Mocking res

To test a route controller or middleware function you also need to mock a response object.

Do this with:

const res = mockResponse(options)

The options can be anything you wish to attach or override in the request.

The vanilla mockResponse gives you the following functions, in the form of sinon spies and stubs.

app: {},
headersSent: false,
locals: {},
append: spy(),
attachment: spy(),
clearCookie: spy(),
download: spy(),
end: spy(),
format: spy(),
json: spy(),
jsonp: spy(),
links: spy(),
location: spy(),
redirect: spy(),
render: spy(),
send: spy(),
sendFile: spy(),
sendStatus: spy(),
set: spy(),
setHeader: spy(),
type: spy(),
get: stub(),
getHeader: stub(),
cookie: stub().returns(res), // returns itself, allowing chaining
status: stub().returns(res), // returns itself, allowing chaining
vary: stub().returns(res) // returns itself, allowing chaining

Note you can always add other spies or stubs as needed via the options.

Example

Let's say you have a route controller like this:

const save = require('../../utils/saveThing') // assume this exists.

const createThing = async (req, res) => {
  const { name, description } = req.body
  if (!name || !description) throw new Error('Invalid Properties')
  const saved = await save({ name, description })
  res.json(saved)
}

To unit test this you could use Mocha, Chai, Sinon, and Proxyquire as follows:

const { expect } = require('chai')
const { stub, match } = require('sinon')
const { mockRequest, mockResponse } = require('mock-req-res')
const proxyquire = require('proxyquire')

describe('src/api/things/createThing', () => {
  const mockSave = stub()

  const createThing = proxyquire('../../src/api/things/createThing', {
    '../../utils/saveThing': mockSave
  })

  const res = mockResponse()

  const resetStubs = () => {
    mockSave.resetHistory()
    res.json.resetHistory()
  }

  context('happy path', () => {
    const name = 'some name'
    const description = 'some description'

    const req = mockRequest({ body: { name, description } })
    const expected = { name, description, id: 1 }
    before(async () => {
      save.returns(expected)
      await createThing(req, res)
    })

    after(resetStubs)

    it('called save with the right data', () => {
      expect(save).to.have.been.calledWith(match({ name, description }))
    })

    it('called res.json with the right data', () => {
      expect(res.json).to.have.been.calledWith(match(expected))
    })
  })

  // and also test the various unhappy path scenarios.
})

See also

• The Express Request object — req
• The Express Response object - res

Development

Branches

Branch	Status	Coverage	Audit	Notes
develop				Work in progress
main				Latest stable release

Development Prerequisites

• NodeJS. I use nvm to manage Node versions — brew install nvm.

Test it

• npm test — runs the unit tests.
• npm run test:unit:cov — runs the unit tests with code coverage

Lint it

npm run lint

Contributing

Please see the contributing notes.