การใช้งาน spy ใน Jest

export const doubleSum = (x: number, y: number): number => {
  const sum = add(x, y)
  return x + y + sum
}

export const add = (x: number, y: number): number => {
  return x + y
}

import * as calculate from './calculate'

describe('spy self', () => {
  it('Should be called add when call doubleSum', () => {
    const x = 2
    const y = 2

    const mathAddSpy = jest.spyOn(calculate, 'add')

    calculate.doubleSum(x, y)

    expect(mathAddSpy).toHaveBeenCalled()
  })
})

import * as calculate from './calculate'

describe('spy self', () => {
  afterEach(() => {
    // restore the spy created with spyOn
    jest.restoreAllMocks()
  })

  it('Should be called add when call doubleSum', () => {
    const x = 2
    const y = 2

    const mathAddSpy = jest.spyOn(calculate, 'add')

    calculate.doubleSum(x, y)

    expect(mathAddSpy).toHaveBeenCalledTimes(1)
  })
})

export const add = (x: number, y: number): number => x + y

import { add } from '../math'

export const doubleSum = (x: number, y: number): number => {
  const sum = add(x, y)
  return x + y + sum
}

import { doubleSum } from './calculate'
import * as math from './math'

describe('spy', () => {
  afterEach(() => {
    // restore the spy created with spyOn
    jest.restoreAllMocks()
  })

  it('Should be called add when call doubleSum', () => {
    const x = 2
    const y = 2

    const mathAddSpy = jest.spyOn(math, 'add')

    doubleSum(x, y)

    expect(mathAddSpy).toHaveBeenCalledTimes(1)
  })

  it('Should be return 9 when call doubleSum and send 2, 2', () => {
    const x = 2
    const y = 2
    const actual = 9

    // ใช้ spyOn ในการทำ Mock / Stub ได้
    jest.spyOn(math, 'add').mockImplementation(() => 5)

    const result = doubleSum(x, y)

    expect(result).toBe(actual)
  })
})

import _ from 'lodash'

export const getUserByUserName = (keyword: string) => {
  var users = [
    { user: 'barney', birthday: '1980-01-01', age: 47 },
    { user: 'fred', birthday: '1990-01-01', age: 37 },
    { user: 'pebbles', birthday: '2000-01-01', age: 27 }
  ]

  const index = _.findIndex(users, (o) => {
    return o.user == keyword
  })

  return users[index]
}

import _ from 'lodash'
import { getUserByUserName } from './user'

describe('Spy library', () => {
  it('Should be called from findIndex with spy', () => {
    const keyword = 'barney'

    const findIndexSpy = jest.spyOn(_, 'findIndex').mockReturnValue(2)

    getUserByUserName(keyword)

    expect(findIndexSpy).toHaveBeenCalled()
  })

  it('Should be return user info from keyword with spy', () => {
    const keyword = 'barney'

    jest.spyOn(_, 'findIndex').mockReturnValue(2)

    const actual = getUserByUserName(keyword)

    // expect(findIndexSpy).toHaveBeenCalled()
    expect(actual).toMatchObject({
      user: 'pebbles',
      birthday: '2000-01-01',
      age: 27
    })
  })
})