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ai-for-dummies/.agents/skills/visual-regression/SKILL.md
T
Marcos Paulo 580293867d refactor: retire the hand-written site
Deletes the pre-Astro pages, scripts, and stylesheets that the migration
replaced, and moves the ones it did not replace out of the way.

Deleted (32 files): app.js, responsive.css, landing.css, rules/app.js,
rules/styles.css, skills/app.js, the ten route index.html files, and the
root hands-on/ copy, which is byte-identical to public/hands-on/ -- the
one the build actually ships.

Moved to legacy/ (12 files): styles.css, full-guide/audit.css,
chapters.css, skills/styles.css, skills-review/styles.css,
skills-review/change-lens.css, and the skills-review/app.js module graph.
These are not dead. The Astro pages import them and the build fails
without them, which the plan had not accounted for. They go to legacy/
rather than src/ because check-tokens.mjs sweeps src, and these files are
full of raw hex and unnamed breakpoints: moving one into src/ should mean
migrating it to tokens in the same change, not adding a scan exclusion.
The prettier, stylelint, and eslint ignore lists that already named these
files at their old paths now name legacy/ instead.

verify.mjs no longer reads app.js. The 102 Portuguese strings were
extracted from its translations.pt object before deletion into
.agents/snapshots/full-guide-pt.json -- a legacy capture, not a snapshot
of the Astro build, so the assertion still compares against an
independent source. The brace-matching helper's assertion is replaced by
one that rejects an empty snapshot entry, without which trimming the
snapshot would make the presence check pass vacuously. Count stays at 84.

audit-ui.mjs reads the ten pages from dist/ and resolves Astro's
base-absolute hrefs against it.

Before deleting anything, rendered-text-diff was run across all ten
routes plus both Portuguese pages: every one at parity, 0 missing and 0
extra. That comparison is not repeatable once the legacy files are gone.
computed-style-diff on /full-guide/ stays at 32 differences, so the moves
are style-neutral.

Docs updated to match: README, AGENTS.md, GATES.md, the architecture
context, the operations guide's lab instructions, and the three skills
that told you to serve the vanilla site.

Publishing is not part of this commit.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-09-06 08:30:27 +00:00

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2.5 KiB
Markdown

---
name: visual-regression
description:
Prove a refactor did not change how the site looks. Use before and after any
page migration, token consolidation, or breakpoint change on ai-for-dummies.
---
# Visual regression
"Maintain the same styles" is a testable claim. Test it.
## Capture
The repo already has a Playwright pattern (`scripts/inspect.py`). Extend it
rather than inventing one.
```python
from playwright.sync_api import sync_playwright
ROUTES = ['/', '/full-guide/', '/summary/', '/models/', '/agents/',
'/skills/', '/rules/', '/skills-review/',
'/hands-on/starter/', '/hands-on/rules/']
WIDTHS = [560, 800, 1100, 1600]
with sync_playwright() as p:
browser = p.chromium.launch(headless=True)
for route in ROUTES:
for w in WIDTHS:
page = browser.new_page(viewport={'width': w, 'height': 900})
page.goto(f'{BASE}{route}', wait_until='networkidle')
page.screenshot(path=f'{OUT}/{route.strip("/").replace("/","_") or "index"}-{w}.png',
full_page=True)
page.close()
browser.close()
```
Run once against `pnpm run preview`. To compare against the vanilla site, serve
a pre-cutover worktree on :4173 first — those files are no longer on `main`.
Keep both sets.
## Compare
```bash
for f in before/*.png; do
compare -metric AE "$f" "after/$(basename $f)" null: 2>&1 # ImageMagick
echo " <- $(basename $f)"
done
```
Pixel-exact is not the bar — antialiasing differs. Judge by eye where the metric
is non-trivial, and attach the pair to the task report.
## The three widths that catch the most
- **560px** — where the 16 ad-hoc breakpoints collapse to `--bp-sm`. Highest
risk in the whole migration.
- **800px** — the most common existing breakpoint; layout flips here.
- **1600px** — `min-width` rules that only fire on large screens are the ones
nobody notices are broken.
Also screenshot at the **old** breakpoint values you removed (520, 530, 600,
620, 720, 850, 880, 900), not just the new ones. Regressions hide exactly there.
## What a real difference looks like
Expect and accept: sub-pixel text shifts, antialiasing.
Investigate: anything that moves by more than ~2px, any colour change (that is a
token bug), any element that appears or disappears (that is content loss — stop
and check the snapshot diff).
## Reduced motion
Capture one pass with `prefers_reduced_motion='reduce'`. Animations must land in
their correct end state, not vanish.