Use native Chrome for Reddit login handoff

tests/login-status.test.ts

@@ -1,6 +1,6 @@
 import express from 'express';
 import type { AddressInfo } from 'node:net';
-import { afterEach, describe, expect, it } from 'vitest';
+import { afterEach, describe, expect, it, vi } from 'vitest';
 import { classifyRedditSessionError } from '../src/browser/client.js';
 import { createLoginRouter } from '../src/web/routes/login.js';
 
@@ -14,6 +14,14 @@ async function request(app: express.Express, path: string): Promise<Response> {
   return fetch(`http://127.0.0.1:${port}${path}`);
 }
 
+async function post(app: express.Express, path: string): Promise<Response> {
+  const server = app.listen(0);
+  servers.push(server);
+  await new Promise<void>((resolve) => server.once('listening', resolve));
+  const { port } = server.address() as AddressInfo;
+  return fetch(`http://127.0.0.1:${port}${path}`, { method: 'POST' });
+}
+
 afterEach(async () => {
   await Promise.all(
     servers.splice(0).map(
@@ -105,4 +113,27 @@ describe('Reddit session status', () => {
     ).toBe('unreachable');
     expect(classifyRedditSessionError(new Error('login form was not found'))).toBe('login-required');
   });
+
+  it('starts a native Chrome login handoff without controlling the attached page', async () => {
+    const requestNativeLogin = vi.fn();
+    const getPage = vi.fn();
+    const invalidate = vi.fn();
+    const app = express();
+    app.use(createLoginRouter({
+      services: {
+        accountAuth: { invalidate },
+        browser: { getPage },
+        nativeLogin: { request: requestNativeLogin },
+      },
+      logger: { info: vi.fn(), error: vi.fn() },
+    } as never));
+
+    const response = await post(app, '/login/start');
+
+    expect(response.status).toBe(202);
+    expect(await response.json()).toEqual({ ok: true, restarting: true });
+    expect(invalidate).toHaveBeenCalledWith('Native Reddit login requested');
+    expect(requestNativeLogin).toHaveBeenCalledOnce();
+    expect(getPage).not.toHaveBeenCalled();
+  });
 });