JEST(unit testing), integration testing, UI testing

https://www.valentinog.com/blog/jest/

implement in project

vue+ts+jest

https://github.com/vuejs/vue-test-utils-typescript-example  學這個安裝
https://github.com/adamsynnott/ts-vue-jest 學這個安裝，一直沒法接受<string>等等的寫法，呈現SyntaxError: /Users/starlord/Desktop/portal/unknown: Unexpected token的錯誤，似乎parse倒哪去了也不知道
https://cli.vuejs.org/config/#babel . ctrl+f5 搜尋jest，並搭配下面這個
https://cli.vuejs.org/migrating-from-v3/#vue-cli-plugin-unit-jest

What's the difference between faking, mocking, and stubbing?https://stackoverflow.com/questions/346372/whats-the-difference-between-faking-mocking-and-stubbing?rq=1

https://ithelp.ithome.com.tw/articles/10187403 Iron man



// functions.test.js or functions.spec.js
const functions = import(./functions)

//beforeAll(), afterAll()
beforeEach(()=>initDatabase());
afterEach(()=>closeDatabase());

const initDatabase = () =>console.log('Database Initialized...');
const closeDatabase = () =>console.log('Database Closed...');

// describe限制beforeEach,...的作用域
describe('描述這個作用域中的動作目的', () =>{
    beforeEach(() => initDatabase());

    test('anything to describe this test', () => {
       const user ="Jeff";
       expect(user).not.toBe("David")
    })
})

test('anything to describe this test', () => {   // test也可以寫成it
   expect(functions.add(2,2)).toBe(4)
})

test('anything to describe this test', () => {
   expect(functions.add(2,2)).not.toBe(5)
})

// toBeNull()
// toBeUndefined() 
// 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

test('anything to describe this test', () => {
   expect(functions.isNull()).toBeNull()
})

// object or array use toEqual() not toBe(), because they are reference types not primitive types, but toEqual()  also can use on primitive types
test('anything to describe this test', () => {
   expect(functions.createUser()).toEqual({
       firstName:'Ni',
       lastName:'diiff'
   })
})

// toBeLessThanOrEqual()
// toBeGreaterThan()
test('anything to describe this test', () => {
   const a=800;
   const b=700;
   expect(a+b).toBeLessThan(1600)
})

// Regex
test('anything to describe this test', () => {
   expect('team').toMatch(/I/)
})

// Arrays
test('anything to describe this test', () => {
   usernames = ['join', 'same', 'admin']
   expect(usernames).toContain('admin')
})

// Promise
test('anything to describe this test', () => {
   expect.assertions(1);  // 斷言接下來有幾個異步執行
   return functions.fetchUser().then(data => {    // 就是個api的動作
      expect(data.name).toEqual('Leanne Graham')
   })
})

//Async Await (等於promise換個寫法！)
test('anything to describe this test', async () => {
   expect.assertions(1);
   const data = await functions.fetchUser();
   expect(data.name).toEqual('David')
})