Ultimate Guide to Mastering Jest Puppeteer

Jest Puppeteer is a powerful tool that combines Puppeteer, a Node library that provides a high-level API to control Chrome or Chromium over the DevTools Protocol, with Jest, a delightful JavaScript Testing Framework with a focus on simplicity. This combination allows developers to write efficient end-to-end tests that simulate user interactions in a real browser environment.

Getting Started with Jest Puppeteer

First, make sure you have Jest and Puppeteer installed in your project:

  
    npm install --save-dev jest puppeteer jest-puppeteer
  

Basic Configuration

Configure Jest to use Puppeteer by adding the following configuration to your jest.config.js file:

  
    module.exports = {
      preset: 'jest-puppeteer',
    };
  

Writing Tests

Here are some common API methods in Jest Puppeteer and their usage:

Example: Launching a Browser

  
    describe('Google', () => {
      beforeAll(async () => {
        await page.goto('https://www.google.com');
      });

      it('should display "google" text on the page', async () => {
        await expect(page).toMatch('google');
      });
    });
  

Example: Taking a Screenshot

  
    it('should take a screenshot', async () => {
      await page.screenshot({ path: 'screenshot.png' });
    });
  

Example: Filling and Submitting a Form

  
    it('should fill and submit a form', async () => {
      await page.type('input[name="q"]', 'Jest Puppeteer');
      await page.click('input[type="submit"]');
      await page.waitForNavigation();
      await expect(page).toMatch('Jest Puppeteer');
    });
  

Example: Element Click

  
    it('should click a button', async () => {
      await page.click('button#example');
      await expect(page).toMatch('Button Clicked');
    });
  

Example: Waiting for Element

  
    it('wait for an element', async () => {
      await page.waitForSelector('div#loaded');
      await expect(page).toMatch('Content loaded');
    });
  

Complete App Example

Here is a comprehensive example using a simple app homepage:

  
    describe('Homepage', () => {
      beforeAll(async () => {
        await page.goto('http://localhost:3000');
      });

      it('should have the correct title', async () => {
        await expect(page.title()).resolves.toMatch('Homepage');
      });

      it('should navigate to About page and display content', async () => {
        await page.click('a[href="/about"]');
        await page.waitForSelector('h1');
        await expect(page).toMatch('About Us');
      });

      it('should fill in a contact form', async () => {
        await page.click('a[href="/contact"]');
        await page.waitForSelector('form');
          
        await page.type('input[name="name"]', 'John Doe');
        await page.type('input[name="email"]', 'john.doe@example.com');
        await page.type('textarea[name="message"]', 'Hello, this is a test message.');
        await page.click('button[type="submit"]');
          
        await page.waitForSelector('.success');
        await expect(page).toMatch('Thank you for your message!');
      });
    });
  

By integrating Jest Puppeteer into your testing workflow, you can automate and ensure a high level of confidence in your web applications, ensuring that they behave as expected in a real user environment.

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