christopherkade

christopherkade

// 1. The method we want to test
function add(x, y) {
  return x + y
}

// 2. A test suite
describe("add method", () => {

  // 3. A unit test
  it("should return 2", () => {

christopherkade

it("should return -2", () => {
  expect(add(0, -2)).toBe(-2)
})

christopherkade

function add(x, y) {
  // Check if the parameters are numbers
  // If not, throw an error
  if (isNaN(x) || isNaN(y)) {
    throw new Error("Parameter is not a number !")
  }
  return x + y
}

describe("add method", () => {  

christopherkade

// /src/setupTests.js

import { configure } from 'enzyme';
import Adapter from 'enzyme-adapter-react-16';

configure({ adapter: new Adapter() });

christopherkade

// App.spec.js
import React from 'react';
import ReactDOM from 'react-dom';
import App from './App';

it('renders without crashing', () => {
  const div = document.createElement('div');
  ReactDOM.render(<App />, div);
  ReactDOM.unmountComponentAtNode(div);
});

christopherkade

PASS src/App.spec.js
 ✓ renders without crashing (2ms)

Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        0.097s, estimated 1s
Ran all test suites.

christopherkade

class App extends Component {
  state = {
    counter: 0
  }

  handleClick = () => {
    this.setState(state => {
      return {
        counter: state.counter + 1
      }

christopherkade

import React from 'react';
import App from './App';
import { shallow } from 'enzyme'

// 1. Test suite
describe("[UNIT] Testing the App component", () => {
  let wrapper

  // 2. A Jest setup helper function  
  beforeEach(() => {

christopherkade

it("should increase counter when the button is clicked", () => {
   wrapper.find("button").simulate("click")
   expect(wrapper.find("h1").text()).toContain("1")
})