FakeExpress

A fake express.js module that could be useful when mocking express objects within any test framework. The module returns an object that resembles an express object.

How to Use

The below example illustrates how the express double could be used for mocking within the jest framework

Test Code on a file called snacksController

const snackService = require('../../services/snacks');

const getSnacks = (req, res, next) => {

  return snackService.getSnacks().then((data) => {
      console.log( "On Success --- " )
      if (data != null)
      {
        res.status(200).json(data);
      }
      }, (error) => {
          res.status(400).json(error);
          console.log( "Service Promise error ", error );
        }
      );
  }

module.exports = { getSnacks };

A test suite for the above snacks controller

// { Request: {}, Response: {}, Router: {}, next: () => {} }
const express = require('fake-express`)

// Mock the response object
const response = jest.genMockFromModule('../../fakes/fakeExpress').Response;


test('get snacks positive test', async () => {
  // Set up
  let snacksData = { name: 'testName', id: 1 };

  snackService.getSnacks.mockResolvedValue(snacksData);
  response.status.mockReturnThis();
  response.json.mockReturnValue(snacksData);

  // Exercise
  await snacksController.getSnacks(null, response, null);

  // Verify
  expect(snackService.getSnacks.mock.calls.length).toBe(1);
  expect(response.status.mock.calls.length).toBe(1);
  expect(response.status.mock.calls[0][0]).toBe(200);
  expect(response.json.mock.calls.length).toBe(1);
  expect(response.json.mock.calls).toEqual([[snacksData]]);
});