Testing Vue.js with Playwright: A Funny Journey to Flawless Web Apps

Playwright is a powerful end-to-end (E2E) testing framework that enables developers to write robust and reliable tests for modern web applications. When used with Vue.js, Playwright can help ensure that your application performs seamlessly across different browsers and devices. Here are some best practices for integrating Playwright with Vue.js effectively.

1. Set Up Playwright with Vue.js

Install Playwright

Before writing tests, install Playwright in your project:

npm install -D @playwright/test

You can also install specific browser dependencies with:

npx playwright install

Configure Playwright

Create a playwright.config.ts or .js file to customize settings like browser types, timeouts, and base URL:

import { defineConfig } from '@playwright/test';

export default defineConfig({
  testDir: './tests/e2e',
  use: {
    baseURL: 'http://localhost:3000',
    headless: true,
    screenshot: 'only-on-failure',
    trace: 'on-first-retry',
  },
});

Integrate with Vue CLI or Vite

Ensure your testing framework knows when your Vue app is ready by adding commands to start and stop the development server.

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2. Organize Your Tests

Maintain a clear structure for your test files to improve readability and maintainability. A common structure is:

project/
├── src/
├── tests/
│   ├── e2e/
│   │   ├── example.spec.ts
│   │   ├── login.spec.ts
│   ├── fixtures/
│   ├── helpers/

• e2e/: Contains Playwright tests.
• fixtures/: Holds reusable test data.
• helpers/: Contains utility functions to reduce repetitive code.

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3. Use Component Testing Before E2E Testing

Leverage tools like Vue Test Utils or Cypress Component Testing to test components in isolation. This helps ensure that individual Vue components are functioning correctly before running more complex E2E tests with Playwright.

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4. Mock APIs and Data

Avoid relying on real backend systems during E2E tests. Use Playwright's route API to intercept network requests and mock responses:

test('loads mock data', async ({ page }) => {
  await page.route('**/api/data', route =>
    route.fulfill({
      status: 200,
      body: JSON.stringify({ key: 'value' }),
    })
  );
  await page.goto('/');
  await expect(page.locator('#data-key')).toHaveText('value');
});

This ensures consistency in test results and speeds up execution.

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5. Leverage Playwright's Selectors

Playwright supports robust selector strategies, including:

• data-testid attributes: Add data-testid attributes to Vue components to make them easier to locate in tests.

  <button data-testid="submit-button">Submit</button>

• Playwright's built-in locators: Use methods like locator() for precise element targeting.

  const button = page.locator('button[data-testid="submit-button"]');

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6. Optimize for Performance and Stability

Use Proper Waits

Avoid relying on fixed timeouts like page.waitForTimeout(1000). Instead, use Playwright’s waitFor utilities to wait for specific conditions:

await page.waitForSelector('text="Welcome"');

Run Tests in Parallel

Playwright supports parallel test execution, which can drastically reduce test time:

npx playwright test --workers=4

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7. Debugging and Troubleshooting

• Screenshots and Traces: Enable screenshots and traces in Playwright's configuration for failed tests. This helps identify issues quickly.

  use: {
    screenshot: 'on',
    trace: 'on',
  },

• Debug Mode: Run Playwright tests in non-headless mode and with verbose logging:

  npx playwright test --headed --debug

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8. CI/CD Integration

Integrate Playwright with your CI/CD pipeline to catch issues early. Ensure the pipeline:

• Installs dependencies.
• Starts the Vue.js development server.
• Runs Playwright tests in a clean environment.

For GitHub Actions, a sample configuration might look like:

name: Playwright Tests

on:
  push:
    branches:
      - main

jobs:
  e2e-tests:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - uses: actions/setup-node@v2
        with:
          node-version: 16
      - run: npm install
      - run: npm run build
      - run: npm run start &
      - run: npx playwright test

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9. Handle Vue.js-Specific Features

Router Navigation

Ensure you wait for navigation to complete when interacting with Vue Router:

await Promise.all([
  page.waitForNavigation(),
  page.click('text="Go to Details"'),
]);

Reactive State

Verify changes in the DOM resulting from Vue's reactivity system:

await page.fill('input[name="name"]', 'John');
await expect(page.locator('.greeting')).toHaveText('Hello, John!');

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10. Continuously Improve Tests

• Regularly update tests to align with new features or changes in the app.
• Monitor flaky tests and fix root causes rather than ignoring them.
• Share Playwright best practices with your team to maintain consistency.