Deploying Playwright with Vercel for Effective End-to-End Testing

Playwright is a powerful framework for browser automation. If you’re using Vercel, you can use Playwright for tasks such as browser tests or generating PDFs.

This guide will go through using the two together, with examples of writing tests for a smooth CI/CD pipeline integration.

Getting Started with Playwright

Playwright is a node library developed by Microsoft, enabling developers to automate Chromium, Firefox, and WebKit with a single API. It offers capabilities like testing across browser contexts and capturing screenshots, making it a versatile tool for end-to-end testing.

1. Installation

Begin by running npm i -D playwright in your project directory to install Playwright as a developer dependency.

2. Initialize a Project

Create a playwright.config.js file to configure your tests. An example configuration could specify different browsers or headless modes.

module.exports = {
  projects: [
    {
      name: 'Chromium',
      use: { browserName: 'chromium' },
    },
    {
      name: 'Firefox',
      use: { browserName: 'firefox' },
    },
    {
      name: 'WebKit',
      use: { browserName: 'webkit' },
    },
  ],
};

3. Connect Playwright to a pool of separately hosted browsers

During development, it will be fine to run a browser on your machine. But for production, you will want to host the browsers outside of Vercel to avoid issues such as file-size and memory limits.

Managing browsers in the cloud can be challenging. To skip the headaches, you can use Browserless. We host thousands of browsers, which you can connect to  with a simple Playwright.BrowserType.connect() method.

// Connecting to Chromium locally
const browser = await playwright.chromium.launch();

// Connecting to Chromium via Browserless
const browser = await playwright.chromium.connect(`https://production-sfo.browserless.io/firefox/playwright?token=GOES_HERE`);

});

Check out the docs for more detail.

Understanding Vercel for Deployment

Vercel is a cloud platform for static sites and Serverless Functions that fits perfectly with your GitHub workflow. It allows for automatic deployments, custom domains, and secure HTTPS, making it an ideal choice for modern web applications.

Creating a Vercel Project:

1. Sign Up: Register or log in to your Vercel account and connect it with your GitHub repository for easy deployment.
2. Project Configuration: Through the Vercel dashboard, configure your project settings, including environment variables and build commands. Since this article is not on vercel project configuration, you can visit the official Vercel resource center if you need help.

Integrating Playwright with Your Vercel Project

To ensure your application's integrity post-deployment, integrating Playwright tests into your Vercel project is essential.

Example Playwright Test Script:

const { test, expect } = require('@playwright/test');

test('verify homepage title', async ({ page }) => {

  await page.goto('https://your-vercel-app.com');

  await expect(page).toHaveTitle(/Expected Title/);

});

Running Tests on Deployment:

Incorporate your tests into your deployment pipeline using Vercel's GitHub integration, ensuring tests are automatically executed on each push. Below, I will specify how to use GitHub actions to accomplish this.

Writing Effective Playwright Tests

Creating practical end-to-end tests with Playwright involves following best practices that ensure your tests are reliable, maintainable, and provide valuable feedback. Here is a list of guidelines for crafting effective tests:

1. Prioritize Key User Flows

Focus on critical paths your users will take, such as signing up, logging in, or completing a purchase. These flows are crucial for your application's success and should be thoroughly tested.

2. Use Descriptive Test Names and Comments

Clearly named tests and well-commented code make your test suite easy to understand and maintain. This is particularly important as your test suite grows and more developers contribute to the codebase. Adopt a naming convention that briefly describes what each test does. Use comments to explain complex test logic or why certain assertions are necessary, making the tests self-documenting.

3. Emulate Real User Interactions

Your tests should mimic how actual users interact with your application, including clicks, typing, scrolling, and navigating across pages. Utilize Playwright’s API to simulate real user behaviors. For instance, instead of directly setting the value of an input field, use the page.type() method to simulate typing.

4. Handle Asynchronous Behavior

Modern web applications often load data asynchronously, leading to race conditions in tests if incorrectly handled. Leverage Playwright’s capabilities to wait for elements to be visible or for network requests to be complete before proceeding with the test. This ensures your tests are stable and reflect real-world usage.

5. Isolate Tests and Ensure Clean State

Each test should run independently without relying on the state of previous tests to avoid flaky behavior. Use Playwright’s hooks (beforeEach, afterEach) to reset the application state between tests. This might include clearing cookies, local storage, or resetting the database to a known state.

6. Optimize Test Speed and Performance

Slow tests can become a bottleneck in the development process, especially when integrated into a CI/CD pipeline. Minimize sleep or wait commands by relying on Playwright’s auto-wait features. Parallelize tests when possible and use headless mode for faster execution.

7. Incorporate Visual Testing When Necessary

Some issues, such as CSS glitches, might not affect functionality but could degrade the user experience. Use Playwright’s screenshot capabilities for visual regression testing. Compare screenshots of key pages over time to catch and fix visual discrepancies.

8. Regularly Review and Refactor Tests

As your application evolves, so should your tests. Regularly reviewing and refactoring tests ensure they remain relevant and maintainable.

Advanced Test Scenario:

// Test for user login functionality

const { test, expect } = require('@playwright/test');

test('user login', async ({ page }) => {

  await page.goto('https://your-vercel-app.com/login');

  await page.fill('input[name="username"]', 'testuser');

  await page.fill('input[name="password"]', 'testpass');

  await page.click('text=Login');

  await expect(page).toHaveURL(/dashboard/);

});

Automating Deployment and Testing with Vercel and Playwright

Automation is vital to achieving continuous integration and delivery. Utilizing GitHub Actions, you can automate your deployment to Vercel and execute Playwright tests in your CI/CD pipeline.

GitHub Actions for Continuous Deployment and Testing:

Define a workflow in .github/workflows/deploy-and-test.yml that deploys your application using Vercel and runs your Playwright tests on each push to the main branch.

name: Deploy and Test with Vercel and Playwright

on:

  push:

    branches:

      - main

jobs:

  deploy:

    runs-on: ubuntu-latest

    steps:

      - uses: actions/checkout@v2

      - uses: vercel/action@v20

        with:

          vercel_token: ${{ secrets.VERCEL_TOKEN }}

          vercel_org_id: ${{ secrets.VERCEL_ORG_ID }}

          vercel_project_id: ${{ secrets.VERCEL_PROJECT_ID }}

  test:

    needs: deploy

    runs-on: ubuntu-latest

    steps:

      - uses: actions/checkout@v2

      - name: Install dependencies

        run: npm install

      - name: Run Playwright tests

        run: npx playwright test

Troubleshooting Common Issues

Integrating automated testing into deployment processes can sometimes be challenging. Here are some common issues you might encounter when integrating Playwright with Vercel and how to resolve them:

1. Flaky Tests

Flaky tests are those that produce inconsistent results, passing at times and failing at others, without any changes to the code. These are often due to timing issues, such as tests proceeding before the page has fully loaded.

To mitigate flaky tests, ensure your Playwright scripts wait for necessary elements to load before proceeding. Utilize Playwright's waitForSelector, waitForLoadState, or waitForNavigation functions to synchronize your tests with the app's state.

2. Timeout Errors

Tests might fail due to timeout errors, where actions or assertions take longer than the configured timeout period. This can occur with slow network responses or heavy page elements.

Adjust the timeout settings in your Playwright tests for longer operations. You can globally set timeout durations in your playwright.config.js or individually in test commands using the timeout option.

3. Deployment Failures

Sometimes, your deployment to Vercel might fail due to configuration issues, missing dependencies, or errors in the build script.

Review the deployment logs in Vercel for specific error messages. Ensure all dependencies are correctly listed in your package.json and that build commands are correctly configured in your vercel.json or through the Vercel dashboard.

Enhancing Your Testing Strategy

To elevate the quality of your web application, consider these strategies to enhance your testing with Playwright and Vercel:

1. Cross-Browser Testing

Different browsers may render your application slightly differently, affecting user experience. Cross-browser testing ensures your app works as intended across your audience's browsers.

Utilize Playwright's ability to test across Chromium, Firefox, and WebKit. Configure your playwright.config.js to run tests in multiple browsers and ensure your CI/CD pipeline includes steps for each browser environment.

2. Responsive Testing

With the variety of device sizes and resolutions today, it's crucial to ensure your application is responsive and provides a seamless experience across all devices.

Leverage Playwright's screen emulation capabilities to test your application on different screen sizes. Define multiple viewports in your test scripts or configurations to automatically test a range of device sizes.

3. Visual Regression Testing

Visual regression testing involves capturing screenshots of your application's pages and comparing them over time to detect unintended visual changes.

Incorporate visual regression testing tools compatible with Playwright, such as Percy or Playwright's built-in screenshot comparison features. This helps catch styling issues that functional tests might miss.

To Wrap Up

Merging Playwright's comprehensive testing capabilities with Vercel's seamless deployment process offers a robust solution for today's web developers. By following the steps outlined in this guide, you can ensure your web applications are not only deployed efficiently but are also robust and user-friendly.

To scale up your testing, you will need to have separately hosted browsers. You can host them in your own back end, or simply connect to Browserless.

To get started, go ahead and grab a 7-day trial.