feedback5 WZ: the waitForFunctionLong slicing test counts slices, not milliseconds (test/e2e/client-wait.test.js slicedPage)

Its fake predicate turned true 95 ms after the page was made and the test wanted at least 4 slices of 30 ms. On a loaded
machine the 30 ms timers fire late and merge the slices: the 0.2.0 candidate's full pass got 'sliced (3 calls)'. A
preload that blocks the event loop 9 ms of every 12 reproduces it 5 of 5 times. Now the predicate holds on the 4th call:
exactly 4 calls, each with the same predicate, args and polling, each slice 0–30 ms, and the wait lasted the three
slices (≥ 85 ms). It passes 5 of 5 under that lag and under 25 ms of every 27. A helper that stops at the first
timed-out slice still fails it. A test timing flake, no product change; golden unchanged.

test/e2e/client-wait.test.js

@@ -27,12 +27,34 @@ function fakePage(trueAfter) {
   };
 }
 
+/**
+ * A page whose predicate holds from its `holdsOn`-th waitForFunction call on; each earlier slice times out after its own
+ * timeout, like puppeteer's. Counted in calls, not in wall time: on a loaded machine late timers merge time-based slices
+ * (fakePage(95) with 30 ms slices returned in 3 calls instead of 4 in the 0.2.0 candidate's full pass).
+ */
+function slicedPage(holdsOn) {
+  const calls = [];
+  return {
+    calls,
+    waitForFunction(fn, opts, ...args) {
+      calls.push({ fn, opts, args });
+      const holds = calls.length >= holdsOn;
+      return new Promise((resolve, reject) => {
+        if (holds) setTimeout(() => resolve({ handle: 'ok', args }), 0);
+        else setTimeout(() => reject(timeoutError(opts.timeout)), opts.timeout);
+      });
+    },
+  };
+}
+
 test('a wait longer than one slice keeps polling the same predicate until it holds', async () => {
-  const page = fakePage(95);
+  const page = slicedPage(4);
   const fn = () => true;
-  const got = await waitForFunctionLong(page, fn, { timeout: 1000, polling: 200, slice: 30 }, 'a', 2);
+  const t0 = Date.now();
+  const got = await waitForFunctionLong(page, fn, { timeout: 60_000, polling: 200, slice: 30 }, 'a', 2);
   assert.deepEqual(got, { handle: 'ok', args: ['a', 2] });
-  assert.ok(page.calls.length >= 4, `sliced (${page.calls.length} calls)`);
+  assert.equal(page.calls.length, 4, 'three slices ran out, the fourth held, nothing polled after it');
+  assert.ok(Date.now() - t0 >= 85, `the three slices waited their 30 ms each (${Date.now() - t0} ms)`);
   for (const c of page.calls) {
     assert.equal(c.fn, fn);
     assert.deepEqual(c.args, ['a', 2]);