类方法在 Jest 中不模拟答案

【问题标题】：Class method is not mocking in Jest类方法在 Jest 中不模拟
【发布时间】：2022-02-22 06:40:34
【问题描述】：

我找不到模拟该行的正确方法，我不断收到以下错误消息：

  console.log
    models             // <---- THIS IS A LINE 173

    TypeError: Database.collection(...).onSnapshot is not a function

      172 |     collections.forEach(collection => {
      173 |       console.log(collection)
    > 174 |       Database.collection(collection).onSnapshot(snapshot => {
          |                                       ^
      175 |         console.log('????', snapshot) // <---- I WANT TO MOCK THIS snapshot
      176 |         snapshot.docChanges().forEach(change => {
      177 |           const item = Object.freeze({ id: change.doc.id, ...change.doc.data() })

这是我的测试用例：

test.only('should react when a new record is created', async () => {
    jest.doMock('@google-cloud/firestore', () => jest.fn(() => ({
      collection: jest.fn()
        .mockReturnThis(function () { return this })
        .mockImplementationOnce(function () { return this })
        .mockImplementationOnce(function () { return this })
        .mockImplementationOnce(function () { return this })
        .mockImplementationOnce(function () { return this })
        .mockImplementationOnce(function () { return this })
        .mockImplementationOnce(function () { return this })
        .mockImplementationOnce(function () { return this })
        .mockImplementationOnce(function () { return this })
        .mockImplementationOnce(function () { return this })
        .mockImplementationOnce(function () { return this })
        .mockResolvedValueOnce(() => { // <---- AT THIS POINT, LINE 174  SHOULD BE MOCKED
          return {
            onSnapshot: jest.fn().mockReturnValue({
              snapshot: []
            })
          }
        }),
      get: jest.fn().mockResolvedValue({ docs: [] }),
      doc: jest.fn().mockReturnThis(),
      set: jest.fn().mockReturnThis(),
      limit: jest.fn().mockReturnThis(),
      onSnapshot: jest.fn().mockReturnThis().mockImplementationOnce(function () { return this }),
      select: jest.fn().mockReturnThis()
    })))

    const StatisticsService = require('./index')
    await StatisticsService()
  })

我应该使用什么来模拟该快照的结果？我也试过了，但没有成功：

.mockImplementationOnce({ docs: [] })
.mockResolvedValueOnce({ docs: [] })

【问题讨论】：

标签： node.js unit-testing google-cloud-firestore jestjs

【解决方案1】：


test('should react when a new record is created', async () => {
    jest.doMock('@google-cloud/firestore', () => {
      const mChanges = [
        {
          type: 'added',
          doc: {
            id: 'MOD_1234',
            data: () => ({
              sku: 'SKU_1234',
              model: 'MOD_1234',
              updatedAt: {
                _seconds: Math.round(Date.now() / 1000) + 1000
              }
            })
          }
        }
      ]
      const mSnapshot = {
        docChanges: jest.fn().mockReturnValue(mChanges)
      }

      return jest.fn(() => ({
        collection: jest.fn().mockReturnThis(),
        get: jest.fn().mockResolvedValue({ docs: [] }),
        doc: jest.fn().mockReturnThis(),
        set: jest.fn().mockReturnThis(),
        limit: jest.fn().mockReturnThis(),
        onSnapshot: jest.fn().mockImplementation(callback => {
          callback(mSnapshot)
        })
      }))
    })

    const Service = require('./index')
    const Module = new Service()

    jest.spyOn(Module, 'onDatabaseRecordCreated')

    const consoleLog = jest.spyOn(console, 'log').mockImplementation()
    await Module.init()
    consoleLog.mockRestore()

    expect(Module.onDatabaseRecordCreated).toHaveBeenCalled()
  })

使用71115363 作为此答案的参考并进行一些修改。

【讨论】：