Launches a browser for the given config.browser type. For chromium: connects via CDP to the pre-launched Chrome (fast path) or falls back to chromium.launch() if pre-launch failed. For firefox/webkit: uses playwright's standard launch (requires npx playwright install [browser]).

Launches a Playwright browser (or reuses an existing one), starts the web server, and returns the page/server/browser connection object.

Whether a page console message prints without --debug. Warnings and errors do, so CI logs capture browser-side failures; other levels are debug-only. Firefox also reports its own parser diagnostics as warnings — [JavaScript Warning: "unreachable code after return statement" …], about the bundle rather than anything the page said, and on every run — so those are debug-only.

The three fields launch actually reads. Narrower than Config on purpose: qunitx run has a config of its own with no test files in it, and asking it to fake thirty unrelated fields to borrow the CDP pre-launch fast path would be a cast pretending to be a type.