Bind Reddit and Matrix session identities

tests/reddit-session-exporter.test.ts

@@ -1,5 +1,8 @@
 import { describe, expect, it } from 'vitest';
-import { createSessionExportDownload } from '../extensions/reddit-session-exporter/session-export.js';
+import {
+  assertMatchingSessionIdentity,
+  createSessionExportDownload,
+} from '../extensions/reddit-session-exporter/session-export.js';
 
 describe('createSessionExportDownload', () => {
   it('creates a JSON data URL that Chrome can download from a service worker', () => {
@@ -49,3 +52,19 @@ describe('createSessionExportDownload', () => {
     expect(() => createSessionExportDownload([], null)).toThrow(/Reddit Chat/i);
   });
 });
+
+describe('assertMatchingSessionIdentity', () => {
+  it('accepts a Matrix user bound to the current Reddit account ID', () => {
+    expect(() => assertMatchingSessionIdentity(
+      { username: 'bot-account', accountId: 'bot' },
+      '@t2_bot:reddit.com',
+    )).not.toThrow();
+  });
+
+  it('rejects a stale Matrix capture from another Reddit account', () => {
+    expect(() => assertMatchingSessionIdentity(
+      { username: 'bot-account', accountId: 't2_bot' },
+      '@t2_other:reddit.com',
+    )).toThrow(/Reload Reddit Chat after switching accounts/);
+  });
+});