Clarify behavioral test scope and stabilize Brooks import test

docs/test-policy.md

@@ -5,6 +5,13 @@ describe an observable outcome, execute the real behavior being checked, and fai
 when that outcome changes. A new runner or a large mocking framework is not
 required for this policy.
 
+These principles also apply to backend services, workers, CLIs, and libraries.
+This file defines their userscripts implementation: Node/JSDOM/Playwright tools,
+the `user ` title prefix, source coverage scope, critical modules, and browser
+validation are repository contracts. Other repositories define equivalent checks
+for their own entrypoints and infrastructure. Shared agent guidance alone does
+not establish that another repository's existing tests or CI already comply.
+
 Use the Node version pinned by `.nvmrc`. The relevant commands are:
 
 | Command | Evidence |
@@ -24,6 +31,12 @@ the current live Binance DOM or grant permission for financial actions.
 
 ## Behavior Names and Stages
 
+Before changing production behavior, write or identify its Given/When/Then
+acceptance scenario with executable setup, an action, and an observable expected
+result. For a regression, first add or identify a test that fails for the observed
+problem, then make the same scenario pass. Review checks the business meaning;
+lint checks the stage structure and cannot prove test-first development order.
+
 All Node test files and `e2e/**/specs/**/*.pw.js` scenarios use a title beginning with
 `user `. Describe the observable behavior in the rest of the title. A
 parameterized title such as `` `user sees ${quantity} accepted orders` `` keeps a

test/unit/brooks-media-import-index.test.js

@@ -1,6 +1,6 @@
 import test from 'node:test';
 import assert from 'node:assert/strict';
-import { mkdir, mkdtemp, readFile, rm, writeFile } from 'node:fs/promises';
+import { mkdir, mkdtemp, readFile, rm, utimes, writeFile } from 'node:fs/promises';
 import { join } from 'node:path';
 import { tmpdir } from 'node:os';
 import {
@@ -62,6 +62,9 @@ test('user observes that Brooks media index import moves the latest completed ex
     const latestPath = join(downloadsDir, 'brooks-media-index-2026-06-03 (1).json');
     await writeFile(oldPath, JSON.stringify(createIndex('2026-06-03T09:00:00.000Z'), null, 2));
     await writeFile(latestPath, JSON.stringify(createIndex('2026-06-03T10:42:15.123Z'), null, 2));
+    // Filesystems can coalesce sequential write mtimes, so model the browser download order explicitly.
+    await utimes(oldPath, new Date('2026-06-03T09:00:00.000Z'), new Date('2026-06-03T09:00:00.000Z'));
+    await utimes(latestPath, new Date('2026-06-03T10:42:15.123Z'), new Date('2026-06-03T10:42:15.123Z'));
 
     // When the importer resolves the appropriate report destination
     const result = await importLatestBrooksMediaIndex({ downloadsDir, reportsDir });