如何使用 jest/enzyme 模拟 multer 以使用 axios post mock call 进行文件上传

Question

我正在使用axios 对后端的调用后测试我的快速路由器。我收到 500 响应而不是 200，不确定如何有效地模拟 multer。 对此有什么想法吗？谢谢

routes.jsx

const axios = require('axios')
const router = express.Router()
const multer = require('multer')
const FormData = require('form-data')
const express = require('express')

const upload = multer({ storage: multer.memoryStorage() }).any()

router.post('/', upload, (req, res) => {
  const formData = new FormData()
   const { body } = req 
    req.files.forEach(file => {
      formData.append(
        'files',
        file.buffer,
        {
          filename: file.originalname
        },
        file.originalname
      )
    })


  axios
    .post('/api/endpoint', formData)
    .then(response => {return response
    })
    .catch(e => {
    console.log(e)
    })
})

module.exports = router

下面是我的测试用例

routes.jsx.test

const axios = require('axios')
const MockAdapter = require('axios-mock-adapter')
const myroute = require('myroute')
const app = express()
const mock = new MockAdapter(axios)
const request = require('supertest')
const express = require('express')
const bodyParser = require('body-parser')
const multer = require('multer')
jest.mock('multer')

multer.mockImplementation(() => {
  return {
    any () {
      return (req, res, next) => {
        req.body = { userName: 'testUser' }
        req.files = [
          {
            originalname: 'sample.name',
            mimetype: 'sample.type',
            path: 'sample.url'
          }
        ]
        return next()
      }
    }
  }
})
app.use(bodyParser.json())

app.use('/', myroute)

describe('sendFiles', () => {
  const url = '/api/endpoint'  

  test('200 response', () => {
    const myMockRes = { mykey: 'myVal' }
    let formData = new FormData()
    const file = new Blob(['somee contents'], { type: 'multipart/form-data' })
    formData.append('files', file)
    formData.append('userName', 'testUser')
    mock.onPost(url).reply(200, myMockRes)
    return (
      request(app)
        .post('/')
        .send({ userName: 'testUser', files: [file] })
        //.expect('Content-Type', /json/)
        .expect(200)
        .then(response => {
          const { data } = response.body
          expect(data).toEqual(myMockRes)
        })
    )
  })


})

错误：

TypeError: Cannot read property 'any' of undefined in routes.jsx

const upload = multer({ storage: multer.memoryStorage() }).any()
    

Answer 1

当您使用jest.mock('multer') 时，Jest 会自动模拟模块并在测试中调用它时返回undefined。由于我们还想模拟 memoryStorage 和 any 方法，因此我们必须通过将工厂作为第二个参数传递给 jest.mock 来显式地做到这一点。

jest.mock('multer', () => {
  const multer = () => ({
    any: () => {
      return (req, res, next) => {
        req.body = { userName: 'testUser' }
        req.files = [
          {
            originalname: 'sample.name',
            mimetype: 'sample.type',
            path: 'sample.url',
            buffer: Buffer.from('whatever'), // this is required since `formData` needs access to the buffer
          },
        ]
        return next()
      }
    },
  })
  multer.memoryStorage = () => jest.fn()
  return multer
})

另一个问题是 Blob 在 Node.js 中不存在。您可以使用Buffer.from 生成缓冲区以在请求中发送。

const file = Buffer.from('whatever')

而且你不需要在测试中使用FormData。

整个代码：

// router.test.js

const axios = require('axios')
const MockAdapter = require('axios-mock-adapter')
const express = require('express')
const app = express()
const mock = new MockAdapter(axios)
const request = require('supertest')

const bodyParser = require('body-parser')

const myroute = require('./router')

jest.mock('multer', () => {
  const multer = () => ({
    any: () => {
      return (req, res, next) => {
        req.body = { userName: 'testUser' }
        req.files = [
          {
            originalname: 'sample.name',
            mimetype: 'sample.type',
            path: 'sample.url',
            buffer: Buffer.from('whatever'),
          },
        ]
        return next()
      }
    },
  })
  multer.memoryStorage = () => jest.fn()
  return multer
})

app.use(bodyParser.json())

app.use('/', myroute)

describe('sendFiles', () => {
  const url = '/api/endpoint'

  test('200 response', () => {
    const myMockRes = { mykey: 'myVal' }
    const file = Buffer.from('whatever')
    mock.onPost(url).reply(200, myMockRes)
    return request(app)
      .post('/')
      .send({ userName: 'testUser', files: [file] })
      .expect(200)
      .then((response) => {
        const { data } = response.body
        expect(data).toEqual(myMockRes)
      })
  })
})