Skill: Visual Testing

Overview

This skill manages visual regression testing:

• Screenshot comparison
• Cross-browser visual testing
• Responsive viewport testing
• Component snapshot testing
• Visual diff analysis

Purpose

Detect unintended visual changes. Use this skill:

• Before UI releases
• After CSS/design changes
• For component library updates
• In CI/CD pipelines

Execution Flow

1. DETECT visual testing tool
2. CONFIGURE viewports and browsers
3. CAPTURE snapshots
4. COMPARE with baselines
5. GENERATE diff report
6. REQUIRE approval for changes

Input Parameters

Parameter	Type	Description	Required
tool	string	percy, chromatic, playwright	No
viewports	string[]	Viewport sizes to test	No
updateBaseline	boolean	Update baselines	No

Supported Tools

Tool	Type	Command
Percy	Cloud	npx percy exec -- npx playwright test
Chromatic	Cloud	npx chromatic
Playwright	Local	npx playwright test --project=visual
Loki	Local	npx loki

Output Format

# Visual Test Report

**Date:** [timestamp]
**Tool:** Percy
**Duration:** 2m 15s

## Snapshot Summary

| Status | Count |
|--------|-------|
| ✅ No Changes | 42 |
| 🔄 Changed | 3 |
| ➕ Added | 2 |
| ➖ Removed | 0 |
| **Total** | **47** |

## Changed Snapshots (Require Review)

### 1. Login Page - Mobile (375px)
- **Diff:** 2.3% pixels changed
- **Browser:** Chromium
- **Status:** ⏳ Pending approval
- **View:** https://percy.io/diff/abc123

**Detected Changes:**
- Button position shifted down 5px
- Error message styling changed

### 2. Dashboard - Desktop (1280px)
- **Diff:** 0.5% pixels changed
- **Browser:** Firefox
- **Status:** ⏳ Pending approval
- **View:** https://percy.io/diff/abc124

## New Snapshots

### 1. Settings Page - Desktop (1280px)
- **Status:** ✅ Auto-approved (new page)

### 2. Profile Page - Mobile (375px)
- **Status:** ✅ Auto-approved (new page)

## Viewports Tested

| Viewport | Width | Snapshots |
|----------|-------|-----------|
| Mobile | 375px | 15 |
| Tablet | 768px | 15 |
| Desktop | 1280px | 17 |

## Coverage

| Category | Count |
|----------|-------|
| Pages | 8 |
| Components | 25 |
| States | 14 |

## Approval Required

3 snapshots require review before merge.
Review at: https://percy.io/builds/12345

Example Usage

Example 1: Run Visual Tests

USER: /visual-test

SKILL OUTPUT:
# Visual Test Report

**Date:** 2026-02-17
**Tool:** Percy
**Duration:** 2m 15s

## Snapshot Summary

✅ 42/47 snapshots unchanged
🔄 3 snapshots changed (review required)
➕ 2 new snapshots added

## Changed Snapshots

### 1. Login Page - Mobile
**Diff:** 2.3%

Before → After comparison shows:
- Button moved down 5px
- Input field border changed

[View Diff](https://percy.io/diff/abc123)

## Action Required

Review 3 changed snapshots in Percy:
https://percy.io/builds/12345

Example 2: Update Baselines

USER: /visual-test --update-baseline

SKILL INPUT:
{
    "updateBaseline": true
}

SKILL OUTPUT:
# Visual Test Report

**Date:** 2026-02-17
**Mode:** Update Baselines

## Baselines Updated

| Snapshot | Previous | Updated |
|----------|----------|---------|
| Login Page - Mobile | v1.2.0 | v1.3.0 |
| Dashboard - Desktop | v1.2.0 | v1.3.0 |
| Settings Page - Tablet | v1.2.0 | v1.3.0 |

⚠️ Baseline updates committed to repository.
Team will see these as the new expected state.

Example 3: Component Testing

USER: /visual-test --component Button

SKILL OUTPUT:
# Visual Test Report - Button Component

**Date:** 2026-02-17
**Component:** Button

## Button States Tested

| State | Viewport | Status |
|-------|----------|--------|
| Default | Mobile | ✅ No change |
| Default | Desktop | ✅ No change |
| Hover | Mobile | ✅ No change |
| Hover | Desktop | ✅ No change |
| Focus | Mobile | ✅ No change |
| Focus | Desktop | ✅ No change |
| Disabled | Mobile | ✅ No change |
| Disabled | Desktop | ✅ No change |
| Loading | Mobile | ✅ No change |
| Loading | Desktop | ✅ No change |

## All Button States Match Baseline ✅

Configuration

Percy Config

// percy.config.js
module.exports = {
    version: 2,
    snapshot: {
        widths: [375, 768, 1280],
        minHeight: 1024,
        percyCSS: `
            .timestamp { visibility: hidden; }
            .random-avatar { visibility: hidden; }
        `,
    },
};

Playwright Visual Config

// playwright.visual.config.ts
import { defineConfig } from '@playwright/test';

export default defineConfig({
    expect: {
        toHaveScreenshot: {
            maxDiffPixels: 100,
            maxDiffPixelRatio: 0.01,
        },
    },
    use: {
        viewport: { width: 1280, height: 720 },
    },
});

Masking Dynamic Content

// Mask elements that change between runs
await expect(page).toHaveScreenshot('dashboard.png', {
    mask: [
        page.locator('.timestamp'),
        page.locator('.live-chart'),
        page.locator('.notification-badge'),
    ],
    maskColor: '#ff00ff',
});

Best Practices

1. Stable Environment: Same fonts, disable animations
2. Mask Dynamic Content: Hide timestamps, random data
3. Consistent Viewports: Standard mobile/tablet/desktop
4. Review Workflow: Approve/reject changes promptly
5. Baseline Management: Version control baselines

CI/CD Integration

# GitHub Actions
name: Visual Tests

on: [push, pull_request]

jobs:
    visual:
        runs-on: ubuntu-latest
        steps:
            - uses: actions/checkout@v4
            - run: npm ci
            - run: npx percy exec -- npx playwright test
              env:
                  PERCY_TOKEN: ${{ secrets.PERCY_TOKEN }}

Integration

This skill integrates with:

• e2e-testing: Combined E2E + visual tests
• visual-regression-agent: Visual analysis
• ui-ux-designer: Design review for changes