Test your knowledge: Testing, Debugging & the Future

Question 1 of 6

In Playwright, how do you assert a beacon was sent?

Same truth as the Service Worker lesson: beacons ride the fetch pipeline.

Answer options A page.on('beacon') — a dedicated beacon event B page.route('**/collect', …) — beacons are fetches, so request interception sees them C Reading the network log from disk after the run D Mocking navigator.sendBeacon before load only

page.route() (or page.waitForRequest) intercepts beacon requests like any fetch — match the collector glob, assert method POST and the body, optionally fulfill with 204. The route pattern '**/collect' is the recipe's canonical form.

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Question 2 of 6

In Chrome DevTools' Network panel, beacons appear…

The initiator type exists internally but the Network UI never surfaces it.

Answer options A under a dedicated 'Beacon' filter type B under Fetch/XHR with a Script initiator — there is NO beacon filter; 'Preserve log' is required across navigations C only in the Performance panel D never — beacons are hidden from DevTools

Beacons land in Fetch/XHR with initiator 'Script' (the fetch group's 'beacon' initiator type is not exposed in the UI). To see page-death beacons you must enable Preserve log BEFORE navigating — the #1 debugging gotcha the lesson fixes.

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Question 3 of 6

How do you test the 64 KiB silent-drop path?

The quota is per fetch group: your test page owns the whole pool.

Answer options A Throttle the network in DevTools and watch for red rows B Fill the pool with synthetic in-flight keepalive requests, then assert sendBeacon returns false and the queue defers C Set a Chrome flag lowering the quota to 1 KiB D You cannot — quota behavior is untestable

The fixture sends pending fetch(keepalive) requests sized to nearly fill 64 KiB, then calls sendBeacon — the boolean flips false without any console error. Asserting the false return AND the queue's retry-when-drained behavior proves the silent path end to end.

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Question 4 of 6

Testing beacon lifecycle timing reliably requires…

The spec's trigger is the STATE, and the automation protocol can set the state directly.

Answer options A real beforeunload dialogs the tester accepts B driving the visibility state directly (CDP Page.setWebLifecycleState / Emulation.setVisibility) and waiting for the flush, not the event C setTimeout-based approximations of page death D reloading the page in a loop until beacons appear

CDP's Page.setWebLifecycleState (frozen/active) and Emulation.setVisibility drive the exact state transitions the spec keys on. Waiting for visibilitychange (the event) races the flush; waiting for the state + the request assertion does not.

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Question 5 of 6

What does the curriculum identify as sendBeacon's likely successor trajectory?

The Fetch standard's deferred fetching section is where the platform's scheduling story continues — the Beacon spec adds no options bag.

Answer options A A WebAssembly telemetry API B The Deferred Fetch family — fetchLater() and its follow-ons — absorbing the beacon use case with bigger budgets and browser-owned scheduling C XMLHttpRequest keepalive revival D Nothing — sendBeacon is terminal and frozen

fetchLater's browser-owned scheduling and termination-based firing point one direction: deferred fetch absorbing fire-and-forget telemetry for new designs. The Beacon API stays (universal, tiny, guaranteed flush on hidden) — feature-detect fetchLater and prefer it where it ships.

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Question 6 of 6

The `test-fixture.ts` recipe provides…

It is the series' capstone test tool — the deterministic stand-in for page death.

Answer options A a reference collector page + intercepted-routes harness reproducing quota, lifecycle, and CORS-silent-drop scenarios deterministically B a physical device lab for mobile process-death testing C golden-file snapshots of Chroma-highlighted beacons D a Visual Studio Code debugger configuration

The fixture wires a Playwright-intercepted collector, synthetic quota pressure, and CDP-driven lifecycle states into one harness: every failure mode the series documents (silent drop, false return, double flush, restore ping) becomes an assertable, deterministic test.

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Test your knowledge: Testing, Debugging & the Future