使用Mocha / chai / sinon进行单元测试Express-如何测试res.send对象的形状？

Question

I am unit testing the individual components that lead up to an API response, in other words, I'm testing it independently of a route since every route runs through this component

I need to test that the function responsible for sending my express response is the correct shape, but without sending an actual HTTP request I can't figure out how to test it.

Here is my component

'use strict'

const moment = require('moment')
module.exports = (req, res, payload) => {
  try {
    let data = []
    if (payload.token) data.push({ token: payload.token })
    data.push({ [payload.resource]: payload.data })
    res.send({
      status: 'OK',
      recordCount: payload.data.length,
      startTimestamp: req.start.toDate(),
      endTimestamp: moment().toDate(),
      timeTaken: moment().toDate().getTime() - req.start.toDate().getTime(),
      data: data
    })
  } catch (error) {
    return res.status(500).json({
      errors: [{
        location: 'n/a',
        param: 'n/a',
        msg: 'something happened when generating the response'
      }]
    })
  }
}

here is my current test ...

const chai = require('chai')
const sinonChai = require('sinon-chai')
const { mockReq, mockRes } = require('sinon-express-mock')
const moment = require('moment')
const present = require('../../src/lib/present')

chai.use(sinonChai)

describe('unit test the present lib method', () => {
  it('should return the expected shape', (done) => {
    const req = mockReq({
      start: moment().toDate(),
      body: {}
    })
    const res = mockRes()
    const shape = present(req, res, {
      resource: 'empty_array',
      data: []
    })
    shape.should.have.own.property('data') // doesnt work
    // AssertionError: expected { Object (append, attachement, ...) } to have own property 'data'
    done()
  })
})

Answer 1

To properly test schema of response you need to do E2E test, which requires you, to send an API call.

If you want to test just logic, inside of the route, you can always extract it to some service, and just test this service.

You can read the following article: https://www.freecodecamp.org/news/how-to-mock-requests-for-unit-testing-in-node-bb5d7865814a/