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Basé sur la classification professionnelle SOC
name Visual Regression Testing description Visual regression testing skill using Playwright, covering screenshot comparison, visual diff thresholds, responsive testing, baseline management, and CI integration. version 1.0.0 author thetestingacademy license MIT tags ["visual-regression","screenshot","playwright","visual-diff","responsive","baseline"] testingTypes ["visual","e2e"] frameworks ["playwright"] languages ["typescript"] domains ["web"] agents ["claude-code","cursor","github-copilot","windsurf","codex","aider","continue","cline","zed","bolt"]
Visual Regression Testing Skill
You are an expert QA engineer specializing in visual regression testing with Playwright. When the user asks you to write, review, or debug visual regression tests, follow these detailed instructions.
Core Principles
Pixel-perfect baselines -- Baseline screenshots are the source of truth for visual correctness.Deterministic rendering -- Eliminate sources of visual non-determinism (animations, fonts, dynamic data).Threshold-based comparison -- Allow small acceptable differences to reduce false positives.Responsive coverage -- Test key breakpoints, not just desktop resolution.Component and page level -- Test both individual components and full page layouts.
Project Structure
tests/
visual/
pages/
homepage.visual.spec.ts
login.visual.spec.ts
dashboard.visual.spec.ts
components/
navigation.visual.spec.ts
footer.visual.spec.ts
card.visual.spec.ts
responsive/
homepage.responsive.spec.ts
checkout.responsive.spec.ts
utils/
visual-helpers.ts
mask-helpers.ts
visual.config.ts
snapshots/ <-- baseline screenshots (committed to git)
homepage-chromium.png
login-chromium.png
playwright.config.ts
Configuration
import { defineConfig, devices } from '@playwright/test' ;
export default defineConfig ({
testDir : './tests/visual' ,
snapshotDir : './tests/snapshots' ,
snapshotPathTemplate : '{snapshotDir}/{testFileDir}/{testFileName}-snapshots/{arg}{-projectName}{ext}' ,
fullyParallel : true ,
retries : 0 ,
use : {
baseURL : 'http://localhost:3000' ,
screenshot : 'only-on-failure'
trace
'retain-on-failure'
expect
toHaveScreenshot
maxDiffPixels
100
maxDiffPixelRatio
0.01
threshold
0.2
animations
'disabled'
toMatchSnapshot
maxDiffPixelRatio
0.01
projects
name
'chromium'
use
'Desktop Chrome'
launchOptions
args
'--font-render-hinting=none'
'--disable-skia-runtime-opts'
name
'firefox'
use
'Desktop Firefox'
name
'webkit'
use
'Desktop Safari'
name
'mobile-portrait'
use
'iPhone 13'
name
'tablet'
use
'iPad Pro 11'
Writing Visual Tests
Full Page Screenshots import { test, expect } from '@playwright/test' ;
test.describe ('Homepage Visual Tests' , () => {
test.beforeEach (async ({ page }) => {
await page.goto ('/' );
await page.waitForLoadState ('networkidle' );
});
test ('homepage should match baseline' , async ({ page }) => {
await expect (page).toHaveScreenshot ('homepage-full.png' , {
fullPage : true ,
animations : 'disabled' ,
});
});
test ('homepage above-the-fold should match baseline' , async ({ page }) => {
await expect (page).toHaveScreenshot ('homepage-above-fold.png' , {
fullPage : false ,
});
});
test ('homepage with content loaded should match baseline' , async ({ page }) => {
await page.getByRole ('heading' , { name : 'Featured Products' }).waitFor ();
await page.waitForSelector ('img[src*="product"]' , { state : 'visible' });
await expect (page).toHaveScreenshot ('homepage-loaded.png' , {
fullPage : true ,
});
});
});
Component-Level Screenshots test.describe ('Navigation Visual Tests' , () => {
test ('desktop navigation should match baseline' , async ({ page }) => {
await page.goto ('/' );
const nav = page.getByRole ('navigation' , { name : 'Main' });
await expect (nav).toHaveScreenshot ('nav-desktop.png' );
});
test ('navigation hover state should match baseline' , async ({ page }) => {
await page.goto ('/' );
const productsLink = page.getByRole ('link' , { name : 'Products' });
await productsLink.hover ();
await expect (page.getByRole ('navigation' )).toHaveScreenshot ('nav-hover.png' );
});
test ('navigation dropdown should match baseline' , async ({ page }) => {
await page.goto ('/' );
await page.getByRole ('button' , { name : 'Account' }).click ();
const dropdown = page.getByRole ('menu' );
await expect (dropdown).toHaveScreenshot ('nav-dropdown.png' );
});
});
State-Based Visual Tests test.describe ('Form Visual States' , () => {
test ('empty form should match baseline' , async ({ page }) => {
await page.goto ('/register' );
await expect (page.locator ('form' )).toHaveScreenshot ('form-empty.png' );
});
test ('form with validation errors should match baseline' , async ({ page }) => {
await page.goto ('/register' );
await page.getByRole ('button' , { name : 'Submit' }).click ();
await page.getByText ('Email is required' ).waitFor ();
await expect (page.locator ('form' )).toHaveScreenshot ('form-errors.png' );
});
test ('form with filled data should match baseline' , async ({ page }) => {
await page.goto ('/register' );
await page.getByLabel ('Name' ).fill ('John Doe' );
await page.getByLabel ('Email' ).fill ('john@example.com' );
await page.getByLabel ('Password' ).fill ('SecurePass123!' );
await expect (page.locator ('form' )).toHaveScreenshot ('form-filled.png' );
});
test ('disabled button state should match baseline' , async ({ page }) => {
await page.goto ('/register' );
const button = page.getByRole ('button' , { name : 'Submit' });
await expect (button).toHaveScreenshot ('button-disabled.png' );
});
});
Responsive Visual Tests test.describe ('Responsive Layout Tests' , () => {
const viewports = [
{ name : 'mobile' , width : 375 , height : 667 },
{ name : 'tablet' , width : 768 , height : 1024 },
{ name : 'desktop' , width : 1280 , height : 720 },
{ name : 'wide' , width : 1920 , height : 1080 },
];
for (const viewport of viewports) {
test (`homepage at ${viewport.name} (${viewport.width} x${viewport.height} )` , async ({ page }) => {
await page.setViewportSize ({ width : viewport.width , height : viewport.height });
await page.goto ('/' );
await page.waitForLoadState ('networkidle' );
await expect (page).toHaveScreenshot (`homepage-${viewport.name} .png` , {
fullPage : true ,
});
});
}
});
Handling Dynamic Content
Masking Dynamic Elements test ('dashboard should match baseline with dynamic content masked' , async ({ page }) => {
await page.goto ('/dashboard' );
await expect (page).toHaveScreenshot ('dashboard.png' , {
mask : [
page.locator ('[data-testid="current-time"]' ),
page.locator ('[data-testid="user-avatar"]' ),
page.locator ('[data-testid="notification-count"]' ),
page.locator ('.chart-container' ),
page.locator ('.ad-banner' ),
],
fullPage : true ,
});
});
Replacing Dynamic Content test ('profile page should match baseline' , async ({ page }) => {
await page.goto ('/profile' );
await page.evaluate (() => {
document .querySelectorAll ('[data-testid="timestamp"]' ).forEach ((el ) => {
el.textContent = 'January 1, 2024' ;
});
const nameEl = document .querySelector ('[data-testid="user-name"]' );
if (nameEl) nameEl.textContent = 'Test User' ;
document .querySelectorAll ('.random-recommendation' ).forEach ((el ) => el.remove ());
});
await expect (page).toHaveScreenshot ('profile-page.png' , {
fullPage : true ,
});
});
Disabling Animations test.beforeEach (async ({ page }) => {
await page.addStyleTag ({
content : `
*, *::before, *::after {
animation-duration: 0s !important;
animation-delay: 0s !important;
transition-duration: 0s !important;
transition-delay: 0s !important;
scroll-behavior: auto !important;
}
` ,
});
});
Waiting for Fonts test ('page with custom fonts should match baseline' , async ({ page }) => {
await page.goto ('/' );
await page.evaluate (() => document .fonts .ready );
await page.waitForTimeout (500 );
await expect (page).toHaveScreenshot ('page-with-fonts.png' );
});
Baseline Management
Updating Baselines
npx playwright test --update-snapshots
npx playwright test tests/visual/homepage.visual.spec.ts --update-snapshots
npx playwright test --project=chromium --update-snapshots
Baseline Workflow ## Baseline Update Process
1. **Intentional change:** Developer modifies UI deliberately
2. **Visual tests fail:** CI detects the visual difference
3. **Review the diff:** Download artifacts, inspect the visual diff
4. **Approve the change:** If the change is intended:
a. Run `npx playwright test --update-snapshots` locally
b. Commit the updated baseline screenshots
c. Push and verify CI passes
5. **Reject the change:** If the change is unintended:
a. Revert the code change causing the visual difference
b. Verify visual tests pass again
Git LFS for Baselines
git lfs install
git lfs track "tests/snapshots/**/*.png"
git lfs track "tests/snapshots/**/*.jpg"
git add .gitattributes
git commit -m "Track visual baselines with Git LFS"
Visual Diff Analysis
Understanding Diff Output When a visual test fails, Playwright generates three images:
test-results/
homepage-visual-spec-ts/
homepage-full-chromium-expected.png <-- Baseline (what it should look like)
homepage-full-chromium-actual.png <-- Current (what it looks like now)
homepage-full-chromium-diff.png <-- Diff (highlighted differences)
Custom Diff Thresholds
test ('brand logo should be pixel-perfect' , async ({ page }) => {
await page.goto ('/' );
const logo = page.locator ('[data-testid="brand-logo"]' );
await expect (logo).toHaveScreenshot ('brand-logo.png' , {
maxDiffPixels : 0 ,
threshold : 0 ,
});
});
test ('blog listing visual check' , async ({ page }) => {
await page.goto ('/blog' );
await expect (page).toHaveScreenshot ('blog-listing.png' , {
maxDiffPixelRatio : 0.05 ,
threshold : 0.3 ,
});
});
Dark Mode and Theme Testing test.describe ('Dark Mode Visual Tests' , () => {
test ('homepage in dark mode' , async ({ page }) => {
await page.emulateMedia ({ colorScheme : 'dark' });
await page.goto ('/' );
await expect (page).toHaveScreenshot ('homepage-dark.png' , { fullPage : true });
});
test ('homepage in light mode' , async ({ page }) => {
await page.emulateMedia ({ colorScheme : 'light' });
await page.goto ('/' );
await expect (page).toHaveScreenshot ('homepage-light.png' , { fullPage : true });
});
test ('reduced motion preference' , async ({ page }) => {
await page.emulateMedia ({ reducedMotion : 'reduce' });
await page.goto ('/' );
await expect (page).toHaveScreenshot ('homepage-reduced-motion.png' );
});
});
CI Integration
GitHub Actions for Visual Tests visual-tests:
name: Visual Regression Tests
runs-on: ubuntu-latest
timeout-minutes: 30
container:
image: mcr.microsoft.com/playwright:v1.42.0-jammy
steps:
- uses: actions/checkout@v4
with:
lfs: true
- uses: actions/setup-node@v4
with:
node-version: '20'
cache: 'npm'
- run: npm ci
- name: Run Visual Tests
run: npx playwright test tests/visual/
- name: Upload Visual Diff
if: failure()
uses: actions/upload-artifact@v4
with:
name: visual-diffs
path: |
test-results/**/
retention-days: 14
- name: Comment PR with Visual Diff
if: failure() && github.event_name == 'pull_request'
uses: actions/github-script@v7
with:
script: |
github.rest.issues.createComment({
owner: context.repo.owner,
repo: context.repo.repo,
issue_number: context.issue.number,
body: '## Visual Regression Detected\n\nVisual differences were found. Please download the artifacts to review the diffs.\n\n[View workflow run](${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }})'
});
Best Practices
Disable animations -- CSS animations cause non-deterministic screenshots.Wait for content -- Always wait for dynamic content, images, and fonts to load.Use deterministic data -- Mock API responses to ensure consistent test data.Mask dynamic regions -- Cover timestamps, avatars, and third-party widgets.Test key breakpoints -- Cover mobile, tablet, and desktop at minimum.Set reasonable thresholds -- Too strict causes false positives; too loose misses real bugs.Use consistent environments -- Run visual tests in Docker containers for consistent rendering.Review diffs carefully -- Not every pixel change is a bug; some are expected.Version baselines -- Commit baselines to source control (with Git LFS for large repos).Test component states -- Cover hover, focus, active, disabled, error, and loading states.
Anti-Patterns to Avoid
No animation control -- Animations make screenshots non-deterministic.Testing with live data -- Real API data changes, causing false failures.Zero-pixel tolerance -- Even anti-aliasing differences trigger failures.Full-page screenshots only -- Component-level screenshots catch more specific regressions.Ignoring font loading -- Fonts not loaded produce blank text in screenshots.Not masking dynamic content -- Timestamps and counters change every run.Running visual tests locally only -- Different OS renders fonts differently.Too many visual tests -- Maintain baselines only for critical pages and components.Not reviewing failures -- Auto-updating baselines without review hides real regressions.Missing responsive tests -- Desktop-only visual tests miss mobile layout bugs. 