@jest-mock/express

A lightweight Jest mock for unit testing Express

Getting Started

Installation:

yarn add --dev @jest-mock/express

npm install --save-dev @jest-mock/express

Importing:

import { getMockReq, getMockRes } from '@jest-mock/express'

Usage

Request - getMockReq

getMockReq is intended to mock the req object as easily as possible. In its simplest form you can call it with no arguments to return a standard req with no values.

const req = getMockReq()

To create mock requests with values, you can simply provide them to the function in any order with all being optional. The advantage of this is that it ensures all of the other properties are not undefined.

// an example GET request to retrieve an entity
const req = getMockReq({ params: { id: '123' } })

// an example PUT request to update a person
const req = getMockReq({
  params: { id: 564 },
  body: { firstname: 'James', lastname: 'Smith', age: 34 },
})

Response - getMockRes

getMockRes will provide a res object with Jest mock functions. Chaining has been implemented for the applicable functions.

const { res, next, clearMockRes } = getMockRes()

All of the returned mock functions can be cleared with a single call to mockClear. An alias is also provided called clearMockRes.

const { res, next, clearMockRes } = getMockRes()

beforeEach(() => {
  clearMockRes()
})

It will also provide a mock next function for convenience. That will also be cleared as part of the call to mockClear/clearMockRes.

Example

A full example could be:

const { res, next } = getMockRes()

test('will respond with the entity from the service', async () => {
  // generate a mock request
  const req = getMockReq({ params: { id: 'abc-def' } })

  // provide the mock req, res, and next to check against
  await myController.getEntity(req, res, next)

  expect(res.json).toHaveBeenCalledWith(
    expect.objectContaining({
      id: 'abc-def',
    }),
  )
  expect(next).toBeCalled()
})