feat(core): experimental in-progress steering hints (2 of 2) (#19307)

packages/core/src/config/userHintService.test.ts

@@ -0,0 +1,77 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, vi } from 'vitest';
+import { UserHintService } from './userHintService.js';
+
+describe('UserHintService', () => {
+  it('is disabled by default and ignores hints', () => {
+    const service = new UserHintService(() => false);
+    service.addUserHint('this hint should be ignored');
+    expect(service.getUserHints()).toEqual([]);
+    expect(service.getLatestHintIndex()).toBe(-1);
+  });
+
+  it('stores trimmed hints and exposes them via indexing when enabled', () => {
+    const service = new UserHintService(() => true);
+
+    service.addUserHint('  first hint  ');
+    service.addUserHint('second hint');
+    service.addUserHint('   ');
+
+    expect(service.getUserHints()).toEqual(['first hint', 'second hint']);
+    expect(service.getLatestHintIndex()).toBe(1);
+    expect(service.getUserHintsAfter(-1)).toEqual([
+      'first hint',
+      'second hint',
+    ]);
+    expect(service.getUserHintsAfter(0)).toEqual(['second hint']);
+    expect(service.getUserHintsAfter(1)).toEqual([]);
+  });
+
+  it('tracks the last hint timestamp', () => {
+    const service = new UserHintService(() => true);
+
+    expect(service.getLastUserHintAt()).toBeNull();
+    service.addUserHint('hint');
+
+    const timestamp = service.getLastUserHintAt();
+    expect(timestamp).not.toBeNull();
+    expect(typeof timestamp).toBe('number');
+  });
+
+  it('notifies listeners when a hint is added', () => {
+    const service = new UserHintService(() => true);
+    const listener = vi.fn();
+    service.onUserHint(listener);
+
+    service.addUserHint('new hint');
+
+    expect(listener).toHaveBeenCalledWith('new hint');
+  });
+
+  it('does NOT notify listeners after they are unregistered', () => {
+    const service = new UserHintService(() => true);
+    const listener = vi.fn();
+    service.onUserHint(listener);
+    service.offUserHint(listener);
+
+    service.addUserHint('ignored hint');
+
+    expect(listener).not.toHaveBeenCalled();
+  });
+
+  it('should clear all hints', () => {
+    const service = new UserHintService(() => true);
+    service.addUserHint('hint 1');
+    service.addUserHint('hint 2');
+    expect(service.getUserHints()).toHaveLength(2);
+
+    service.clear();
+    expect(service.getUserHints()).toHaveLength(0);
+    expect(service.getLatestHintIndex()).toBe(-1);
+  });
+});