Testing Visual Regression

What it does

When your agent uses it

• Detecting unintended UI changes
• Pixel differences
• With phrases like test visual changes
• Compare screenshots

Example prompts

• “test visual changes”
• “compare screenshots”
• “detect UI regressions”
• “/testing-visual-regression”

Requirements

• Python 3
• Node.js
• Docker
• Compatibility (from SKILL.md): Designed for Claude Code
• Pre-approved tools (allowed-tools): Read, Write, Edit, Grep, Glob, Bash(test:visual-*)

Workflow steps

7 steps, taken from the first numbered list in SKILL.md.

1. 1Identify all UI components and pages requiring visual coverage using Glob to scan component directories and route definitions.
2. 2Create a visual test file for each component or page
3. 3Capture screenshots with deterministic settings
4. 4Compare captured screenshots against baselines
5. 5For responsive testing, capture at multiple breakpoints
6. 6Review diff images for each failure and classify as
7. 7Integrate into CI so visual tests run on every pull request with diff images uploaded as artifacts.

What it can do on your machine

Read from SKILL.md and the folder at commit 80f86df. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves these tools, so the agent can use them without asking each time:

  • Read
  • Write
  • Edit
  • Grep
  • Glob
  • Bash(test:visual-*)

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Ships 4 files in scripts/ (Python and JavaScript), which the agent can run.

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  Links to these hosts (documentation or services it may open):

  • playwright.dev
  • percy.io
  • chromatic.com
  • github.com
  • reg-viz.github.io

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

• Compatibility

  Designed for Claude Code

  From compatibility in the SKILL.md frontmatter.

Context cost

Testing Visual Regression loads about 1.3k tokens when it runs, and up to ~1.3k if it reads all its reference files. Until then it costs about 64 tokens; SKILL.md has 465 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~64

When it runs · the whole SKILL.md, loaded when a task matches

~1.3k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~1.3k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); the scripts in this folder are not scanned.

SKILL.md

The full file from jeremylongshore/tons-of-skills-marketplace at commit 80f86df, republished under its MIT licence (© jeremylongshore). 465 words, ~1,296 tokens.

name

testing-visual-regression

description

Detect visual changes in UI components using screenshot comparison. Use when detecting unintended UI changes or pixel differences. Trigger with phrases like "test visual changes", "compare screenshots", or "detect UI regressions".

allowed-tools

Read, Write, Edit, Grep, Glob, Bash(test:visual-*)

compatibility

Designed for Claude Code

version

1.25.0

author

Jeremy Longshore <jeremy@intentsolutions.io>

license

MIT

tags

testing, testing-visual

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

test('homepage matches baseline', async ({ page }) => {
  await page.goto('/');
  await page.waitForLoadState('networkidle');
  await page.addStyleTag({ content: '* { animation: none !important; }' });
  await expect(page).toHaveScreenshot('homepage.png', {
    maxDiffPixelRatio: 0.001,
    fullPage: true,
  });
});

{
  "label": "Login Page",
  "url": "http://localhost:3000/login",  # 3000: 3 seconds in ms
  "selectors": ["document"],
  "misMatchThreshold": 0.1,
  "viewports": [
    { "label": "phone", "width": 375, "height": 812 },  # 812: 375 = configured value
    { "label": "desktop", "width": 1280, "height": 720 }  # 1280: 720 = configured value
  ]
}

© jeremylongshore, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 10 other files (scripts, references, assets) in skills/.curated/testing-visual-regression of jeremylongshore/tons-of-skills-marketplace.

• SKILL.md
• assets/README.md
• assets/example_backstop_config.js
• assets/example_chromatic_config.yml
• assets/example_percy_config.yml
• assets/html_report_template.html
• references/README.md
• scripts/README.md
• scripts/analyze_diffs.py
• scripts/run_visual_tests.py
• scripts/update_baselines.py

Open the folder on GitHubat commit 80f86df