jest斷言

York Chen

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Aug 17, 2020

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const employee = {
    makeChange: function(bill, price) {
      return bill - price;
    }
  };
  
  module.exports = employee;

tobe

test('Check the result of  + ', () => {

    //整數可以使用 toBe 或 toEqual 斷言
    expect(1 + 1).toBe(2)
    expect(1 + 2.toBe(8)
    expect(2).toEqual(2)

    //測試輸出值是否大於期望值
    expect(5).toBeGreaterThan(4)

    //測試輸出值是否大於等於期望值
    expect(5).toBeGreaterThanOrEqual(5)

    //測試輸出值是否小於期望值
    expect(5).toBeLessThan(6)

    //測試輸出值是否小於期望值
    expect(5).toBeLessThanOrEqual(5)

    //會忽略些微的誤差
    expect(0.1 + 0.2).toBeCloseTo(0.3)
    //需完全相等
    expect(0.1 + 0.2).toBe(0.3)
})

type

test('Special value',()=>{
    //期望值為 true
    expect(true).toBeTruthy()
    
    //期望值為 false
    expect(false).toBeFalsy()

    //期望值為 null
    expect(null).toBeNull()

    //期望值為 undefined
    expect(undefined).toBeUndefined()

    //期望值為 undefined 之外的值
    expect(null).toBeDefined()
})

toContain

test('For array test in jest',()=>{
    let arrA = ['A','B','C']

    //檢查陣列內是否含有某值
    expect(arrA).toContain('B')
    
    //搭配迴圈檢查每個位置都不等於空
    for(let i in arrA){
        expect(arrA[i]).not.toBe('')
    }
})

toEqual

test('Check the object type', () => {
    let peopleA = {
        name: 'tim'
    }
    peopleA.age = 25

    //測試字串
    expect(peopleA.name).toBe('tim')
    //測試物件
    expect(peopleA).toEqual({ name: 'tim', age: 25 })
    //測試物件
    expect(peopleA).toEqual({ name: 'joy', age: 27 })
    //預防函式回傳某個結果可以使用 not 
    //確認 name 不等於空
    expect(peopleA.name).not.toBe('')
    peopleA.name = ''
    //如果 name 是空的
    expect(peopleA.name).not.toBe('')
})

toMatch_rugex.test

test('Use toMatch test',()=>{
    //搭配正規表達式
    expect('https://www.ec.co.jp/prod/1069433750').toMatch(/prod/)
    expect('https://www.ec.co.jp/p/1069433750').toMatch(/prod/)
}