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test(desktop): distinguish honest truncation from tracer bugs in settle specs

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Blind-review round 10 (Fable high) finding: the specs' settle polls
accepted a legitimately truncated measure — the tracer honestly hitting
its 5s render-wait deadline on a slow box — and then failed the painted-
rows assertion with a message blaming the tracer. Both tests now poll
for clean measures only and fail truncated-only runs with an explicit
harness-timing message.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Signed-off-by: Max Lampert <maxwell@squareup.com>
This commit is contained in:
Max Lampert
2026-08-24 23:51:52 -07:00
parent 116b73bd5e
commit b6f18d0cec
1 changed files with 45 additions and 6 deletions
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51
desktop/tests/e2e/switch-settle-after-paint.spec.ts
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@@ -27,11 +27,18 @@ test("cold-switch settle measure lands only after rows are painted", async ({
// Poll for the settle measure inside the page and — in the same synchronous
// evaluation turn — snapshot what the DOM shows at that moment. Reading the
// DOM from the test process after the fact would race further renders.
// DOM from the test process after the fact would race further renders. Only
// CLEAN measures count: a truncated one means the tracer honestly hit its
// render-wait deadline (harness timing), which must fail with that reason
// rather than masquerading as a tracer regression.
const atSettle = await page.evaluate(async (measureName) => {
const deadline = Date.now() + 15_000;
while (Date.now() < deadline) {
if (performance.getEntriesByName(measureName).length > 0) {
const entries = performance.getEntriesByName(measureName);
const clean = entries.filter(
(entry) => !(entry as PerformanceMeasure).detail?.settleWaitTruncated,
);
if (clean.length > 0) {
return {
renderPending:
document.querySelector('[data-render-pending="true"]') !== null,
@@ -39,13 +46,31 @@ test("cold-switch settle measure lands only after rows are painted", async ({
'[data-message-id^="mock-deep-history-"]',
).length,
settled: true,
truncatedOnly: false,
};
}
if (entries.length > 0) {
return {
renderPending: true,
rowCount: 0,
settled: false,
truncatedOnly: true,
};
}
await new Promise((resolve) => setTimeout(resolve, 16));
}
return { renderPending: true, rowCount: 0, settled: false };
return {
renderPending: true,
rowCount: 0,
settled: false,
truncatedOnly: false,
};
}, SWITCH_MEASURE);
expect(
atSettle.truncatedOnly,
"tracer truncated at its render-wait deadline — harness timing exhausted, not a tracer bug; rerun",
).toBe(false);
expect(atSettle.settled, "switch trace must settle").toBe(true);
expect(
atSettle.rowCount,
@@ -117,23 +142,37 @@ test("settle waits for a delayed lazy channel-pane chunk", async ({ page }) => {
releaseChunk();
// Same in-page polling as above: snapshot the DOM in the evaluation turn
// where the measure first exists.
// where the first CLEAN measure exists. A truncated measure here means the
// released chunk's mount outran the remaining render-wait budget — a
// harness timing exhaustion, and it must fail with that reason.
const atSettle = await page.evaluate(async (measureName) => {
const deadline = Date.now() + 15_000;
while (Date.now() < deadline) {
if (performance.getEntriesByName(measureName).length > 0) {
const entries = performance.getEntriesByName(measureName);
const clean = entries.filter(
(entry) => !(entry as PerformanceMeasure).detail?.settleWaitTruncated,
);
if (clean.length > 0) {
return {
rowCount: document.querySelectorAll(
'[data-message-id^="mock-deep-history-"]',
).length,
settled: true,
truncatedOnly: false,
};
}
if (entries.length > 0) {
return { rowCount: 0, settled: false, truncatedOnly: true };
}
await new Promise((resolve) => setTimeout(resolve, 16));
}
return { rowCount: 0, settled: false };
return { rowCount: 0, settled: false, truncatedOnly: false };
}, SWITCH_MEASURE);
expect(
atSettle.truncatedOnly,
"tracer truncated before the released chunk painted — harness timing exhausted, not a tracer bug; rerun",
).toBe(false);
expect(atSettle.settled, "switch trace must settle after release").toBe(true);
expect(
atSettle.rowCount,