How do you use Jest and Cypress for web development?

1 What is Jest?

Jest is a JavaScript testing framework that is designed to work with any JavaScript project, from React to Vue, Angular, Node, and more. It offers a range of features to make testing easy and enjoyable, such as fast parallel execution, built-in code coverage and mocking support, snapshot testing, interactive watch mode, customizable matchers and assertions, and seamless integration with other tools and libraries. With Jest you can write unit tests, integration tests, and snapshot tests for your web components, logic, and data. Plus, it supports TypeScript, Babel, and webpack so you can use the latest JavaScript features and syntax.

2 What is Cypress?

Cypress is a web testing framework that simplifies and automates end-to-end testing of web applications. It runs in the same browser as your application, allowing it to access and control DOM elements, network requests, local and session storage, cookies, authentication, browser tabs, and windows. With Cypress, you can write end-to-end tests to simulate real user interactions such as filling out forms, navigating between pages, handling alerts and pop-ups, performing drag-and-drop and file upload actions, and testing responsive layouts and accessibility features. Additionally, Cypress provides a user-friendly interface to view tests running live, debug code, and inspect the application state.

3 How to use Jest and Cypress together?

Jest and Cypress are complementary tools that can cover different aspects of testing and debugging your web applications. While Jest is ideal for testing the logic and behavior of your components and functions, Cypress is ideal for testing the user interface and experience of your applications. By using both tools, you can achieve a comprehensive and reliable testing strategy that can ensure the quality and functionality of your web development projects.

To use Jest and Cypress together, you need to install them as dependencies in your project, using either npm or yarn. For example, you can run the following commands in your terminal: npm install --save-dev jest cypress yarn add --dev jest cypress Then, you need to configure them according to your project needs and preferences. For example, you can create a jest.config.js file and a cypress.json file in your project root, where you can specify various options and settings for each tool. You can also use the CLI commands or the GUI interface to run your tests with Jest and Cypress.

4 How to write tests with Jest?

To write tests with Jest, you need to use the describe, test, and expect functions, which are globally available in Jest. The describe function lets you group your tests into logical blocks, the test function lets you define your test cases and expectations, and the expect function lets you make assertions about the values or outcomes of your code. For example, you can write a simple test for a function that adds two numbers like this:

describe('add function', () => {
  test('should return the sum of two numbers', () => {
    expect(add(2, 3)).toBe(5);
  });
});        

You can also use other functions and methods that Jest provides, such as beforeEach, afterEach, beforeAll, afterAll, toBeTruthy, toEqual, toMatchSnapshot, and many more. You can also use mock functions, spy functions, timers, and other features that Jest offers to test different scenarios and behaviors.

5 How to write tests with Cypress?

To write tests with Cypress, you need to use the cy object, which is the core of Cypress and exposes various commands and methods that let you interact with your web application. The cy object follows a chainable syntax, which means you can chain multiple commands together to perform complex actions and assertions. For example, you can write a simple test for a login form like this:

describe('login form', () => {
  it('should log in the user with valid credentials', () => {
    cy.visit('/login'); // go to the login page
    cy.get('#username').type('test'); // type the username
    cy.get('#password').type('test123'); // type the password
    cy.get('#submit').click(); // click the submit button
    cy.url().should('include', '/dashboard'); // check the url
    cy.contains('Welcome, test'); // check the content
  });
});        

You can also use other commands and methods that Cypress provides, such as cy.request, cy.route, cy.fixture, cy.contains, cy.should, cy.wait, and many more. You can also use custom commands, plugins, and other features that Cypress offers to extend and customize your testing experience.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?