| name | chromium-local-smoke-tests |
| description | Pattern for always-on Chromium browser smoke coverage using a deterministic local Edge page plus a stable public-web slice |
| domain | testing |
| confidence | high |
| source | earned |
Context
Use this when the team wants a small, always-on Chromium browser slice that proves real page interaction honestly without creating browser-specific MCP tools.
Pattern
- Prefer Edge + local static HTML for the deterministic slice, then pair it with one stable public-web page for required internet coverage.
- Keep the scope to page content discovery first: landmarks, ARIA-labeled inputs, and buttons.
- Launch Edge as an app window with startup hygiene,
--force-renderer-accessibility, and an isolated --user-data-dir for reliability.
- Keep the public tier to a stable browser-testing page (for example
https://demo.playwright.dev/todomvc/) and assert only long-lived page content such as labeled inputs or links.
- Keep browser chrome, logins, and ambient profile state out of the default slice.
Good first assertions (local tier)
- Landmark or navigation container is discoverable.
- ARIA-labeled search box resolves as
Edit.
- ARIA-labeled primary action resolves as
Button.
Good second-slice assertions (local interaction tier)
- Add one editable field whose value can be typed and read back to prove
ui_type + ui_read.
- Add one always-visible text node to prove baseline
ui_read on Chromium page content.
- Add one page-owned post-click assertion (revealed text, changed text, toggled state) to prove
ui_click affected the DOM, not just that the automation layer returned success.
- Keep the post-click assertion inside the page content itself; avoid browser chrome, URL assertions, tabs, or address bar checks.
Harness implementation note
- Use app-window launch (
--app=) plus accessibility/startup hygiene and an isolated profile, then wait for all page-owned readiness selectors before running assertions. Only if readiness does not appear should the test harness use a narrow, test-only dismissal path for known Edge first-run/sync dialogs; if Stefan's sync popup appears, look specifically for a "Got it" button and dismiss that exact button before proceeding.
- Close the launched Edge window first, then kill the dedicated temp-profile browser process tree only if it fails to exit promptly. Delete the temp profile after teardown.
Good public-site assertions (smoke tier)
- Canonical placeholder or label text as accessible name (e.g., TodoMVC
What needs to be done? → Edit).
- Longstanding links or buttons by visible text + stable control type.
- Prefer public demos maintained by browser/tooling vendors over individual-maintained practice sites.
- Use 15s+ timeouts for public pages (vs 5s local) to absorb network latency.
Anti-patterns
- Do not depend on public practice sites whose copy or uptime is outside your control.
- Do not mix address-bar/tab-strip/browser-chrome assertions into the first slice.
- Do not rely on ambient browser state for default coverage; use an isolated browser profile.
- Do not accept
clickResult.Success == true as sufficient proof of Chromium interaction; require a page-content effect.
