用 jest 测试 Nexts 页面 api 时如何模拟 mongodb 客户端？

Question

我想用 jest 测试一个页面下一页 api 文件，虽然目前测试运行良好，但我遇到了一些问题

1. 每个页面 API POST 请求实际上都是在向 mongo 数据库发送数据，即使我正在运行测试；这是不可取的，因为我不希望在测试此类 POST 请求时将测试数据放在数据库中
2. 在某些情况下，我想模拟 mongo 连接失败，以测试 500 状态错误响应，但我不确定如何执行此操作

我如何模拟 mongoclient 连接，以便在连接成功后测试将项目插入数据库，或故意导致 mongo 客户端连接错误？

    newsletter.ts (PAGE API FILE)
    import type { NextApiRequest, NextApiResponse } from 'next'
import { MongoClient } from 'mongodb'

async function connectDatabase() {
  const client = await MongoClient.connect(<url>)
  return client
}

async function insertDocument(client: MongoClient, document: { email: string }) {
  const db = client.db()
  await db.collection('newsletter').insertOne(document)
}

async function handler(req: NextApiRequest, res: NextApiResponse) {
  const userEmail = JSON.parse(req.body).email
  if (!userEmail || !userEmail.includes('@')) {
    res.status(422).json({ message: 'Invalid email address' })
    return
  }

  let client
  try {
    client = await connectDatabase()

  } catch (error) {
    res.status(500).json({ message: 'Connecting to the database failed!' })
    return
  }

  try {
    await insertDocument(client, { email: userEmail })

  } catch(error) {
    res.status(500).json({ message: 'Inserting data failed!' })
    return
  }

  client.close()

  res.status(201).json({ message: 'Signed up!' })

}

export default handler

这是测试代码

newsletter.test.tsx (PAGE API TEST FILE)

import type { NextApiRequest, NextApiResponse } from 'next'
import {
  createMocks as _createMocks,
  Mocks,
  RequestOptions,
  ResponseOptions,
} from 'node-mocks-http'

import newsletter from '../../pages/api/newsletter'



const createMocks = _createMocks as (
  reqOptions?: RequestOptions,
  resOptions?: ResponseOptions

) => Mocks<NextApiRequest, NextApiResponse>

describe('Test responses for newsletter api', () => {
  it('Should return status 201 with valid request body', async () => {
    const { req, res } = createMocks({
      method: 'POST',
      body: JSON.stringify({
        email: 'abc@email.com',
      }),
    })
    await newsletter(req, res)
    expect(res._getStatusCode()).toBe(201)
    expect(JSON.parse(res._getData())) .toEqual(
      expect.objectContaining({
        message: 'Signed up!',
      })
    )
  })

  it('Should return status 422 with invalid req body', async () => {
    const { req, res } = createMocks({
      method: 'POST',
      body: JSON.stringify({
        email: 'abcemail.com',
      }),
    })
    await newsletter(req, res)
    expect(res._getStatusCode()).toBe(422)
    expect(JSON.parse(res._getData())).toEqual(
      expect.objectContaining({
        message: 'Invalid email address',
      })
    )
  })
})

Answer 1

发现这个answer 帮助我解决了问题

为了模拟 mongoclient，我只需要使用 jest.spyOn，并将用户的所有其他函数链接到数据库中。这也阻止了对服务器的真正调用，并且不再发送测试数据。为了模拟状态 500 错误，我只是模拟了一个被拒绝的承诺。

代码最终变成了这样：

import type { NextApiRequest, NextApiResponse } from 'next'
import {
  createMocks as _createMocks,
  Mocks,
  RequestOptions,
  ResponseOptions,
} from 'node-mocks-http'
import { MongoClient } from 'mongodb'

import newsletter from '../../pages/api/newsletter'



const createMocks = _createMocks as (
  reqOptions?: RequestOptions,
  resOptions?: ResponseOptions
) => Mocks<NextApiRequest, NextApiResponse>
describe('Test responses for newsletter api', () => {

  afterEach(() => {
    jest.resetAllMocks()
  })

  it('Should return status 500 on failure to connect to database', async () => {
    const { req, res } = createMocks({
      method: 'POST',
      //@ts-ignore
      body: JSON.stringify({
        email: 'abc@email.com',
      }),
    })
    const connectSpy = jest.spyOn(MongoClient, 'connect').mockRejectedValueOnce(new Error)
    await newsletter(req, res)
    expect(connectSpy).toHaveBeenCalled()
    expect(res._getStatusCode()).toBe(500)
  })


  it('Should return status 201 with valid request body', async () => {
    const { req, res } = createMocks({
      method: 'POST',
      //@ts-ignore
      body: JSON.stringify({
        email: 'abc@email.com',
      }),
    })
    const insertOne = jest.fn().mockResolvedValueOnce({ acknowleged: true })
    const collection = jest.fn().mockReturnValueOnce({ insertOne })
    const connectSpy = jest.spyOn(MongoClient, 'connect').mockResolvedValueOnce({ db: jest.fn().mockReturnValueOnce({ collection }), close: jest.fn() })
    await newsletter(req, res)
    expect(connectSpy).toHaveBeenCalled()
    expect(res._getStatusCode()).toBe(201)
    expect(JSON.parse(res._getData())) .toEqual(
      expect.objectContaining({
        message: 'Signed up!',
      })
    )
  })

})