Unit test using jest spy and mock implementation

array.sort((x, y) => +new Date(x.createdAt) - +new Date(y.createdAt));

// Get path to resource on disk
 const onDiskPath = vscode.Uri.file( 
   path.join(context.extensionPath, 'css', 'style.css')
);
// And get the special URI to use with the webview
const cssURI = panel.webview.asWebviewUri(onDiskPath);

const sessionMiddleware = expressSession({
    secret: 'Tecky Academy teaches typescript',
    resave:true,
    saveUninitialized:true,
    cookie:{secure:false}
});

app.use(sessionMiddleware);

io.use((socket,next)=>{
    let req = socket.request as express.Request
    let res = req.res as express.Response
    sessionMiddleware(req, res, next as express.NextFunction
});
//...
io.on('connection', function (socket) {
    // You can set any values you want to session here.
    const req = socket.request as express.Request;
    req.session['key'] = 'XXX';
    // There is no auto save for session.
    socket.request.session.save();

    // You can also send data using socket.emit() although it is not very useful
    socket.emit('any-key','values');
    socket.on("disconnect",()=>{
        //... rest of the code
    })
});

const range = (from, to, step) =>
  [...Array(Math.floor((to - from) / step) + 1)].map((_, i) => from + i * step);

range(0, 9, 2);
//=> [0, 2, 4, 6, 8]

// can also assign range function as static method in Array class (but not recommended )
Array.range = (from, to, step) =>
  [...Array(Math.floor((to - from) / step) + 1)].map((_, i) => from + i * step);

Array.range(2, 10, 2);
//=> [2, 4, 6, 8, 10]

Array.range(0, 10, 1);
//=> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

Array.range(2, 10, -1);
//=> []

Array.range(3, 0, -1);
//=> [3, 2, 1, 0]

test('the data is peanut butter', done => {
  function callback(data) {
    expect(data).toBe('peanut butter');
    done();
  }

  fetchData(callback);
});

test('the data is peanut butter', () => {
  expect.assertions(1);
  return fetchData().then(data => {
    expect(data).toBe('peanut butter');
  });
});

"scripts": {
  "test": "jest",
   "start": "node index.js"
},
"devDependencies": {
  "jest": "^26.6.3"
}

const {getIntroduction} = require('./util')

test('should output name and age', () => {
  const text = getIntroduction('Max', 20)
  expect(text).toBe('Max is 20 years old')
})

test('should verify typed', async () => {
  const browser = await puppeteer.launch({
    headless: false,
    slowMo: 10,
    args: ['--window-size=1920,1080']
  })
  const page = await browser.newPage()
  await page.goto(url)
  await page.type('.input-text', 'Hello World!')

  const finalText = await page.$eval('input.input-text', el => el.textContent)
  expect(finalText).toBe(finalText)
})

yarn add --dev jest
yarn add --dev typescript ts-jest @types/jest @types/node ts-node ts-node-dev
yarn ts-jest config:init

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

test('object assignment', () => {
  const data = {one: 1};
  data['two'] = 2;
  expect(data).toEqual({one: 1, two: 2});
});

`toBeNull matches only null
toBeUndefined matches only undefined
toBeDefined is the opposite of toBeUndefined
toBeTruthy matches anything that an if statement treats as true
toBeFalsy matches anything that an if statement treats as false`

{
    "sqltools.connections": [
        {
            "previewLimit": 50,
            "server": "localhost",
            "port": 5432,
            "driver": "PostgreSQL",
            "name": "memo_wall",
            "database": "memo_wall",
            "username": "junowong",
            "password": "gfHK$dgm6501"
        }
    ]
}

// __tests__/helpers.test.js

const { format_date, format_plural } = require('../utils/helpers');


test('format_date() returns a date string', () => {
  const date = new Date('2020-03-20 16:12:03');

  expect(format_date(date)).toBe('3/20/2020');
});

========================

// /utils/helpers.js

module.exports = {
  format_date: (date) => {
    return `${new Date(date).getMonth() + 1}/${new Date(date).getDate()}/${new Date(date).getFullYear()}`;
  },
};