proffesor-for-testing/visual-testing-advanced

Advanced Visual Testing

<default_to_action> When detecting visual regressions or validating UI:

1. CAPTURE baseline screenshots (first run establishes baseline)
2. COMPARE new screenshots against baseline (pixel-by-pixel or AI)
3. MASK dynamic content (timestamps, ads, user counts)
4. TEST across devices (desktop, tablet, mobile viewports)
5. REVIEW and approve intentional changes, fail on regressions

Quick Visual Testing Steps:

• Set up baseline on main branch
• Compare feature branch against baseline
• Mask dynamic elements (timestamps, avatars)
• Use AI-powered comparison to reduce false positives
• Integrate in CI/CD to block visual regressions

Critical Success Factors:

• Functional tests don't catch visual bugs
• AI-powered tools reduce false positives
• Review diffs, don't just auto-approve </default_to_action>

Quick Reference Card

When to Use

• UI component changes
• CSS/styling modifications
• Responsive design validation
• Cross-browser consistency checks

Visual Bug Types

| Bug Type | Description | |----------|-------------| | Layout shift | Elements moved position | | Color change | Unintended color modification | | Font rendering | Typography issues | | Alignment | Spacing/alignment problems | | Missing images | Broken image paths | | Overflow | Content clipping |

Comparison Algorithms

| Algorithm | Best For | |-----------|----------| | Pixel diff | Exact match requirement | | Structural similarity | Handle anti-aliasing | | AI semantic | Ignore insignificant changes |

---

PRIMARY PATH: qe-browser visual-diff

Most visual regression work should go through the qe-browser fleet skill. It wraps Vibium (WebDriver BiDi) and provides pixel-diff against stored baselines with threshold enforcement and diff-image output. See .claude/skills/qe-browser/SKILL.md.

# Navigate
vibium go https://example.com
vibium wait load

# First run — creates baseline in .aqe/visual-baselines/homepage.png
node .claude/skills/qe-browser/scripts/visual-diff.js --name homepage

# Subsequent runs — compare, non-zero exit on mismatch
node .claude/skills/qe-browser/scripts/visual-diff.js --name homepage --threshold 0.02

# Scope to a single region
node .claude/skills/qe-browser/scripts/visual-diff.js --name hero --selector "#hero"

# Responsive — run diff at each breakpoint
for viewport in "375 667" "768 1024" "1920 1080"; do
  read w h <<< "$viewport"
  vibium viewport $w $h
  node .claude/skills/qe-browser/scripts/visual-diff.js --name "homepage-${w}x${h}"
done

# Reset baseline after an intentional design change
node .claude/skills/qe-browser/scripts/visual-diff.js --name homepage --update-baseline

Baselines live in .aqe/visual-baselines/. The script uses pixelmatch when installed, with a hash-based exact-match fallback otherwise. Non-zero exit when similarity < 1 - threshold, so CI gating is $?-based.

When to keep Playwright visual regression

Use the Playwright recipe below only when you need:

• AI semantic comparison (Percy, Applitools) to ignore insignificant pixel drift
• Cross-browser rendering checks in Firefox/WebKit (Vibium is Chrome-only today)
• Tight integration with an existing Playwright test suite

---

LEGACY: Visual Regression with Playwright (fallback)

import { test, expect } from '@playwright/test';

test('homepage visual regression', async ({ page }) => {
  await page.goto('https://example.com');

  // Capture and compare screenshot
  await expect(page).toHaveScreenshot('homepage.png');
  // First run: saves baseline
  // Subsequent runs: compares to baseline
});

test('responsive design', async ({ page }) => {
  // Mobile viewport
  await page.setViewportSize({ width: 375, height: 667 });
  await page.goto('https://example.com');
  await expect(page).toHaveScreenshot('homepage-mobile.png');

  // Tablet viewport
  await page.setViewportSize({ width: 768, height: 1024 });
  await expect(page).toHaveScreenshot('homepage-tablet.png');
});

---

Handling Dynamic Content

test('mask dynamic elements', async ({ page }) => {
  await page.goto('https://example.com');

  await expect(page).toHaveScreenshot({
    mask: [
      page.locator('.timestamp'),     // Dynamic time
      page.locator('.user-count'),    // Live counter
      page.locator('.advertisement'), // Ads
      page.locator('.avatar')         // User avatars
    ]
  });
});

---

AI-Powered Visual Testing (Percy)

import percySnapshot from '@percy/playwright';

test('AI-powered visual test', async ({ page }) => {
  await page.goto('https://example.com');

  // Percy uses AI to ignore anti-aliasing, minor font differences
  await percySnapshot(page, 'Homepage');
});

test('component visual test', async ({ page }) => {
  await page.goto('https://example.com/components');

  // Snapshot specific component
  const button = page.locator('.primary-button');
  await percySnapshot(page, 'Primary Button', {
    scope: button
  });
});

---

Playwright Configuration

// playwright.config.js
export default {
  expect: {
    toHaveScreenshot: {
      maxDiffPixels: 100,      // Allow 100 pixel difference
      maxDiffPixelRatio: 0.01, // Or 1% of image
      threshold: 0.2,          // Color similarity threshold
      animations: 'disabled',  // Disable animations
      caret: 'hide'            // Hide cursor
    }
  }
};

---

Agent-Driven Visual Testing

// Comprehensive visual regression
await Task("Visual Regression Suite", {
  baseline: 'main-branch',
  current: 'feature-branch',
  pages: ['homepage', 'product', 'checkout'],
  devices: ['desktop', 'tablet', 'mobile'],
  browsers: ['chrome', 'firefox', 'safari'],
  threshold: 0.01
}, "qe-visual-tester");

// Returns:
// {
//   comparisons: 27,  // 3 pages × 3 devices × 3 browsers
//   differences: 2,
//   report: 'visual-regression-report.html'
// }

---

Agent Coordination Hints

Memory Namespace

aqe/visual-testing/
├── baselines/*          - Baseline screenshots
├── comparisons/*        - Diff results
├── components/*         - Component snapshots
└── reports/*            - Visual regression reports

Fleet Coordination

const visualFleet = await FleetManager.coordinate({
  strategy: 'visual-testing',
  agents: [
    'qe-visual-tester',   // Screenshot comparison
    'qe-test-executor',   // Cross-browser execution
    'qe-quality-gate'     // Block on visual regressions
  ],
  topology: 'parallel'
});

---

Related Skills

• accessibility-testing - Visual a11y checks
• compatibility-testing - Cross-browser visuals
• regression-testing - Regression suite

---

Remember

Functional tests don't catch visual bugs. Layout shifts, color changes, font rendering, alignment issues - all invisible to functional tests but visible to users.

AI-powered tools reduce false positives. Percy, Applitools use AI to ignore insignificant differences (anti-aliasing, minor font rendering).

With Agents: qe-visual-tester automates visual regression across browsers and devices, uses AI to filter noise, and generates visual diff reports. Catches UI regressions before users see them.