Js 使用jest来进行单元测试

官方网站:  https://github.com/facebook/jest

基本用法

1. npm install --save-dev jest

2. 我们创建一个项目,包含3个文件: 

2.1  package.json : 

{
  "name": "test_jest",
  "version": "1.0.0",
  "description": "this is test_jest project",
  "author": "siwei",
  "private": true,
  "scripts": {
    "test": "jest"
  },
  "dependencies": {},
  "devDependencies": {
    "jest": "^24.9.0"
  },
  "engines": {
    "node": ">= 4.0.0",
    "npm": ">= 3.0.0"
  },
  "browserslist": [
    "> 1%",
    "last 2 versions",
    "not ie <= 8"
  ]
}

2.2 src/sum.js

function sum(a,b){
  return a + b;
}

module.exports = sum;

2.3 test/sum.test.js

const sum = require('../src/sum')

test(' 1 + 2 = 3', () => {
  expect(sum(1,2)).toBe(3)
})

3. 安装: 

$ npm install --dev-save

4. 运行

$ npm run test

(这个命令会把当前目录下的所有  xx.test.js 的文件找到并且运行 ) 

结果如下

> test_jest@1.0.0 test /workspace/test_jest
> jest

 PASS  test/sum.test.js
  ✓  1 + 2 = 3 (8ms)

Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        1.539s
Ran all test suites.

Matcher

参考: https://jestjs.io/docs/en/using-matchers  以及https://jestjs.io/docs/en/expect

expect('..') 返回的叫做 期望 expectation 

toBe(...) 则是叫做 matcher 

用matcher的好处是, 可以打印出详细的log, (断点级别的信息都能看到, 虽然我这辈子都没用过断点)

 我用的最多的是toBe, toEqual