test: prove hidden-tab polling in a real browser

changelog.d/1282-polling-issue-fix.md

@@ -2,3 +2,5 @@
 - Report and guard browser visibility during Transit QA so hidden-page polling pauses cannot masquerade as playback regressions (asturksever, #1282).
 - Require each live city to supply its own feed vehicles in Transit QA; retained vehicles cannot qualify another city (asturksever, #1282).
 - Bound the Transit card-anchor probe by observed poll coverage instead of a fixed 20-second window (asturksever, #1282).
+- Keep visible-page Transit probes focused through the browser testing API (asturksever, #1282).
+- Add a real-browser regression gate for hidden-tab periodic work, explicit refresh, resume and teardown (asturksever, #1282).

docs/CURRENT-STATE.md

@@ -4002,6 +4002,8 @@ animation. Polls, surface completions and trail fades request individual renders
 Disable clears vehicles, detection references, requests, timers and holds;
 destruction also releases collections and registrations.
 
+The `scripts/qa-layer-visibility.mjs` gate uses the development-only registration seam and real browser tab visibility to prove periodic work pauses while hidden, explicit refresh still works, resume performs one overdue refresh, and disabled layers stay stopped.
+
 **Acceptance harness.** Run against an already running development server:
 
 ```sh

scripts/format-scope.json

@@ -1070,5 +1070,6 @@
   "scripts/assemble-changelog.mjs",
   "src/tooling/changelogFragments.test.mjs",
   "src/data/gbfsProxyRateLimit.test.mjs",
-  "src/terrainHeightsBounds.test.mjs"
+  "src/terrainHeightsBounds.test.mjs",
+  "scripts/qa-layer-visibility.mjs"
 ]

scripts/qa-layer-visibility.mjs

@@ -0,0 +1,124 @@
+#!/usr/bin/env node
+/**
+ * Real-browser proof for manager-owned periodic work and document visibility.
+ * Uses the app's development-only layer registration seam; no provider keys.
+ * Run: node scripts/qa-layer-visibility.mjs --url http://localhost:4173
+ * Hiding uses a real background tab, never a patched document.hidden getter.
+ */
+import assert from 'node:assert/strict';
+import puppeteer from 'puppeteer';
+import { chromeExecutablePath } from './qa-chrome.mjs';
+
+const args = process.argv.slice(2);
+const urlIndex = args.indexOf('--url');
+const url = new URL(
+  (urlIndex >= 0 ? args[urlIndex + 1] : undefined) ||
+    process.env.QA_BASE_URL ||
+    'http://localhost:4173',
+);
+url.searchParams.set('welcome', '0');
+const browser = await puppeteer.launch({
+  executablePath: chromeExecutablePath(),
+  headless: true,
+  args: [
+    '--no-sandbox',
+    '--disable-background-timer-throttling',
+    '--disable-renderer-backgrounding',
+  ],
+});
+const pause = (ms) => new Promise((resolve) => setTimeout(resolve, ms));
+const check = (name, actual, expected) => {
+  assert.equal(actual, expected, name);
+  console.log(`PASS ${name}: ${actual}`);
+};
+try {
+  const page = await browser.newPage();
+  const focus = await page.createCDPSession();
+  await focus.send('Emulation.setFocusEmulationEnabled', { enabled: true });
+  await page.goto(url.href, { waitUntil: 'domcontentloaded' });
+  await page.waitForFunction(
+    () => window.__gevQaRegisterLayer && window.__godsEyeView?.dataManager,
+  );
+  await page.evaluate(async () => {
+    const manager = window.__godsEyeView.dataManager;
+    window.__qaVisibilityUpdates = 0;
+    window.__gevQaRegisterLayer(manager, {
+      id: 'qa-document-visibility',
+      name: 'Visibility QA',
+      updateInterval: 750,
+      init() {},
+      enable() {},
+      disable() {},
+      destroy() {},
+      async update() {
+        window.__qaVisibilityUpdates++;
+        return true;
+      },
+      getStats() {
+        return { count: window.__qaVisibilityUpdates };
+      },
+    });
+    await manager.setEnabled('qa-document-visibility', true, { origin: 'qa' });
+  });
+  const count = () => page.evaluate(() => window.__qaVisibilityUpdates);
+  await page.waitForFunction(() => window.__qaVisibilityUpdates >= 3);
+  check('periodic updates run while visible', (await count()) >= 3, true);
+  await focus.send('Emulation.setFocusEmulationEnabled', { enabled: false });
+  const cover = await browser.newPage();
+  await cover.bringToFront();
+  await page.waitForFunction(() => document.visibilityState === 'hidden');
+  const hiddenCount = await count();
+  await pause(2200);
+  check('hidden tab makes no periodic updates', await count(), hiddenCount);
+  check(
+    'explicit refresh remains available while hidden',
+    await page.evaluate(() =>
+      window.__godsEyeView.dataManager.refreshLayer('qa-document-visibility'),
+    ),
+    true,
+  );
+  check('explicit hidden refresh runs once', await count(), hiddenCount + 1);
+  await focus.send('Emulation.setFocusEmulationEnabled', { enabled: true });
+  await page.waitForFunction(
+    () =>
+      document.visibilityState === 'visible' &&
+      window.__qaVisibilityUpdates > 0,
+  );
+  await pause(200);
+  check(
+    'resume performs one overdue refresh without a catch-up burst',
+    await count(),
+    hiddenCount + 2,
+  );
+  await page.evaluate(() =>
+    window.__godsEyeView.dataManager.setEnabled(
+      'qa-document-visibility',
+      false,
+      { origin: 'qa' },
+    ),
+  );
+  const stopped = await count();
+  await focus.send('Emulation.setFocusEmulationEnabled', { enabled: false });
+  await cover.bringToFront();
+  await page.waitForFunction(() => document.visibilityState === 'hidden');
+  await focus.send('Emulation.setFocusEmulationEnabled', { enabled: true });
+  await pause(1100);
+  check(
+    'disabled layer does not resume on visibility change',
+    await count(),
+    stopped,
+  );
+  check(
+    'QA layer destroys cleanly',
+    await page.evaluate(() =>
+      window.__gevQaUnregisterLayer(
+        window.__godsEyeView.dataManager,
+        'qa-document-visibility',
+      ),
+    ),
+    true,
+  );
+  console.log('RESULT: 7 passed');
+} finally {
+  await browser.close();
+}

scripts/qa-transit.mjs

@@ -275,6 +275,10 @@ const browser = await puppeteer.launch({
   ],
 });
 const page = await browser.newPage();
+// This gate measures visible-page motion. OS minimization must not silently
+// switch it into the app's intentional hidden-tab polling pause.
+const focus = await page.createCDPSession();
+await focus.send('Emulation.setFocusEmulationEnabled', { enabled: true });
 boundPageEvaluations(page);
 await page.setViewport({ width: 1920, height: 1080 });
 const pageErrors = [];