Verify Browser

Verify in a Real Browser

UI correctness is not provable by type-check or unit tests alone. A component can compile, pass jsdom tests, and still be misaligned, overflow, throw at runtime, or navigate to the wrong place. This pillar drives a real Chromium against the running app and asserts what the user would see.

The four verification pillars: type-check → unit/integration tests → verify-runtime (data-flow via dev logs) → verify-browser (this one, UI/behavior).

When to Use

• Changed a component's layout, spacing, alignment, or responsive (md:/lg:) behavior.
• Touched navigation/routing, redirects, or click handlers.
• Built a user-facing flow where the golden path + edge cases must be exercised in a browser.
• Any claim of "done" that rests on rendering or interaction, not just data.

Procedure

1. Start the dev server (background) — see run-web for the recipe; .mise.toml pins node, so no PATH prefix is needed:

   nohup pnpm --filter web dev > /tmp/dev.log 2>&1 &
   # confirm: grep "Local:" /tmp/dev.log  -> http://localhost:5173/
   

2. Write a throwaway harness at apps/web/scripts/verify-*.mjs (skeleton below). Assert behavior + layout + console errors; screenshot to /tmp.
3. Run it and read the PASS/FAIL tally; open the screenshots to confirm visually:

   node apps/web/scripts/verify-foo.mjs
   

4. Clean up: delete the throwaway script and stop the server:

   rm -f apps/web/scripts/verify-foo.mjs
   lsof -ti:5173 | xargs kill 2>/dev/null
   

The harness is intentionally throwaway — it encodes this change's assertions, not a permanent test. Promote a check to a real Playwright e2e test only if it guards an ongoing contract.

Harness Skeleton

import { chromium } from '@playwright/test';
const BASE = 'http://localhost:5173';
const out = [];
const errs = [];
const log = (n, ok, d = '') => { out.push(ok); console.log(`${ok ? 'PASS' : 'FAIL'}  ${n}${d ? '  -- ' + d : ''}`); };

// wait for server
for (let i = 0; i < 30; i++) { try { if ((await fetch(`${BASE}/`)).ok) break; } catch {} await new Promise(r => setTimeout(r, 500)); }

const browser = await chromium.launch();
const page = await browser.newPage({ viewport: { width: 1280, height: 1000 } });
page.on('console', m => { if (m.type() === 'error') errs.push(m.text()); });
page.on('pageerror', e => errs.push(e.message));

try {
  await page.goto(`${BASE}/your-route`, { waitUntil: 'networkidle' });
  await page.waitForTimeout(700);

  // --- behavior ---
  const body = await page.locator('body').textContent();
  log('heading renders', (await page.getByRole('heading', { name: '제목' }).count()) > 0);
  await page.getByRole('button', { name: '버튼' }).first().click();
  await page.waitForURL('**/expected', { timeout: 5000 }).catch(() => {});
  log('click routes correctly', new URL(page.url()).pathname === '/expected', page.url());

  // --- layout: no horizontal overflow ---
  const overflow = await page.evaluate(() => document.documentElement.scrollWidth - document.documentElement.clientWidth);
  log('no horizontal overflow', overflow <= 1, `overflowX=${overflow}`);

  await page.screenshot({ path: '/tmp/verify.png', fullPage: true });
  log('no console/page errors', errs.length === 0, errs.slice(0, 5).join(' | '));
} finally {
  await browser.close();
}
const failed = out.filter(x => !x).length;
console.log(`\n=== ${out.length - failed}/${out.length} passed ===`);
if (failed) process.exit(1);

Assertion Recipes

• Click then navigation: await locator.click() then await page.waitForURL('**/x'); assert new URL(page.url()).pathname.
• Visible text / heading: getByRole('heading', { name }), or (await body).includes(text) for loose checks.
• Edge-to-edge alignment (two elements line up): compare boundingBox() — Math.abs(a.x - b.x) <= 1 && Math.abs((a.x+a.width) - (b.x+b.width)) <= 1.
• Sticky/fixed position: in page.evaluate, walk ancestors for getComputedStyle(n).position === 'fixed' and check distance to the viewport edge.
• Navigation isolation (no escape links): iterate a[href] via locators, assert each href is in the allowed set.
• Console/runtime errors: subscribe to console (type error) and pageerror before navigating.

Gotchas (learned the hard way)

• Avoid the $$eval / $eval locator methods — a security hook blocks any literal eval token immediately followed by an open-paren. Use plain locators, or page.evaluate(() => ...) for in-page measurement (the evaluate method name is not flagged).
• Hidden duplicate layouts: responsive code renders both a mobile and desktop tree (block lg:hidden / hidden lg:block), so getByText('X').first() may grab the hidden copy and the click times out. Pick a viewport where only one layout renders (e.g. width < lg for the mobile tree), or scope the locator to the visible container.
• Node toolchain: .mise.toml pins node 22.14.0 (see run-web). If a shell lacks mise it falls to the broken Homebrew node (Abort trap: 6) — run mise install, or prefix with mise exec -- ....
• vitest exit 1 is not always failure: a known Firebase-analytics async rejection fires after env teardown and flips the exit code to 1 even when every test passes. Read the Tests N passed line, not just the exit code.
• cwd drift: a prior cd persists between Bash calls. Use absolute or repo-root-relative paths when running the harness.

Red Flags

• "It type-checks, so the layout is fine." — Compilation says nothing about alignment, overflow, or what renders.
• "The unit test passes." — jsdom has no layout engine; it cannot catch overflow, sticky positioning, or visual regressions.
• "I'll just describe what it should look like." — Take the screenshot and read it. Claims about UI without a rendered artifact are unverified.
• "I can't run a browser." — Say so explicitly and note the verification gap rather than implying the UI was checked.