feat(test): Week 3 质量保障体系 — 55 新增测试 + CI/CD 流水线

前端第二批测试 (42 用例):
- AuthBloc: 16 用例 (启动恢复/登录/注册/角色选择/班级码/登出)
- HomeBloc: 8 用例 (数据加载/今日检测/心情统计/连续天数/离线容错)
- CalendarBloc: 10 用例 (月份切换/日期选择/视图模式/状态保持)
- MoodBloc: 8 用例 (统计加载/周期切换/API解析/错误处理)

后端 P0 单元测试 (13 用例):
- journal_service: 5 用例 (model_to_resp 转换/mood回退/weather回退/tags解析)
- sync_service: 8 用例 (冲突收集/DTO构造/序列化roundtrip/非冲突排除)

CI/CD:
- pr-check.yml: PR 触发 cargo fmt+check+clippy+test + flutter analyze+test
- main-merge.yml: main push 触发完整检查 + cargo audit 安全审计

测试统计: 前端 84 通过, 后端 73 通过 (全部通过)

app/test/features/mood/bloc/mood_bloc_test.dart

@@ -0,0 +1,197 @@
+// MoodBloc 单元测试
+//
+// 覆盖：心情统计加载、周期切换、API 解析、错误处理
+// 使用 mocktail mock ApiClient
+
+import 'package:dio/dio.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:mocktail/mocktail.dart';
+import 'package:nuanji_app/data/models/journal_entry.dart';
+import 'package:nuanji_app/data/remote/api_client.dart';
+import 'package:nuanji_app/features/mood/bloc/mood_bloc.dart';
+
+// ===== Mock =====
+
+class MockApiClient extends Mock implements ApiClient {}
+
+// ===== 测试数据 =====
+
+/// 模拟 API 返回的心情统计数据
+Map<String, dynamic> _mockResponseBody({
+  List<Map<String, dynamic>>? moodCounts,
+  int streakDays = 5,
+  int totalJournals = 12,
+  String? dominantMood = 'happy',
+}) {
+  return {
+    'data': {
+      'mood_counts': moodCounts ??
+          [
+            {'mood': 'happy', 'count': 8, 'percentage': 66.7},
+            {'mood': 'calm', 'count': 3, 'percentage': 25.0},
+            {'mood': 'sad', 'count': 1, 'percentage': 8.3},
+          ],
+      'streak_days': streakDays,
+      'total_journals': totalJournals,
+      'dominant_mood': dominantMood,
+    },
+  };
+}
+
+void main() {
+  late MockApiClient mockApi;
+  late MoodBloc bloc;
+
+  setUpAll(() {
+    registerFallbackValue(Response(requestOptions: RequestOptions()));
+  });
+
+  setUp(() {
+    mockApi = MockApiClient();
+    bloc = MoodBloc(api: mockApi);
+  });
+
+  tearDown(() {
+    bloc.dispose();
+  });
+
+  // ===== 辅助 =====
+
+  /// 配置 mock API.get 返回指定响应体
+  void _stubGet(Map<String, dynamic> body) {
+    when(() => mockApi.get(any(), queryParams: any(named: 'queryParams')))
+        .thenAnswer((_) async => Response(
+              requestOptions: RequestOptions(path: ''),
+              data: body,
+            ));
+  }
+
+  /// 配置 mock API.get 抛出异常
+  void _stubGetError(Object error) {
+    when(() => mockApi.get(any(), queryParams: any(named: 'queryParams')))
+        .thenThrow(error);
+  }
+
+  /// 等待异步 _loadStats 完成
+  Future<void> _waitForAsync() =>
+      Future<void>.delayed(const Duration(milliseconds: 50));
+
+  // ===== 1. load() 设置 isLoading = true =====
+
+  test('load() 立即设置 isLoading = true', () {
+    // 让 API 永不返回，这样 isLoading 会一直保持 true
+    when(() => mockApi.get(any(), queryParams: any(named: 'queryParams')))
+        .thenAnswer((_) async {
+      await Future<void>.delayed(const Duration(seconds: 10));
+      return Response(requestOptions: RequestOptions(path: ''), data: {});
+    });
+
+    bloc.load();
+
+    expect(bloc.state.isLoading, isTrue);
+  });
+
+  // ===== 2. load() 成功 → isLoading = false, stats 有数据 =====
+
+  test('load() 成功后 isLoading = false 且 stats 包含数据', () async {
+    _stubGet(_mockResponseBody());
+
+    bloc.load();
+    await _waitForAsync();
+
+    expect(bloc.state.isLoading, isFalse);
+    expect(bloc.state.errorMessage, isNull);
+    expect(bloc.state.stats.streakDays, 5);
+    expect(bloc.state.stats.totalJournals, 12);
+  });
+
+  // ===== 3. load() 成功 → moodCounts 解析正确 =====
+
+  test('load() 成功后 moodCounts 解析正确', () async {
+    _stubGet(_mockResponseBody());
+
+    bloc.load();
+    await _waitForAsync();
+
+    final counts = bloc.state.stats.moodCounts;
+    expect(counts.length, 3);
+
+    expect(counts[0].mood, Mood.happy);
+    expect(counts[0].count, 8);
+    expect(counts[0].percentage, 66.7);
+
+    expect(counts[1].mood, Mood.calm);
+    expect(counts[1].count, 3);
+    expect(counts[1].percentage, 25.0);
+
+    expect(counts[2].mood, Mood.sad);
+    expect(counts[2].count, 1);
+    expect(counts[2].percentage, 8.3);
+  });
+
+  // ===== 4. load() 成功 → dominantMood 解析正确 =====
+
+  test('load() 成功后 dominantMood 解析正确', () async {
+    _stubGet(_mockResponseBody(dominantMood: 'calm'));
+
+    bloc.load();
+    await _waitForAsync();
+
+    expect(bloc.state.stats.dominantMood, Mood.calm);
+  });
+
+  test('load() dominantMood 为 null 时不崩溃', () async {
+    _stubGet(_mockResponseBody(dominantMood: null));
+
+    bloc.load();
+    await _waitForAsync();
+
+    expect(bloc.state.stats.dominantMood, isNull);
+    expect(bloc.state.errorMessage, isNull);
+  });
+
+  // ===== 5. load() 失败 → errorMessage = '加载统计数据失败' =====
+
+  test('load() API 失败时设置 errorMessage', () async {
+    _stubGetError(Exception('网络错误'));
+
+    bloc.load();
+    await _waitForAsync();
+
+    expect(bloc.state.isLoading, isFalse);
+    expect(bloc.state.errorMessage, '加载统计数据失败');
+  });
+
+  // ===== 6. changePeriod 更新周期并触发加载 =====
+
+  test('changePeriod 更新 selectedPeriod 并触发重新加载', () async {
+    _stubGet(_mockResponseBody(streakDays: 10));
+
+    bloc.changePeriod(StatsPeriod.month);
+    await _waitForAsync();
+
+    expect(bloc.state.selectedPeriod, StatsPeriod.month);
+    expect(bloc.state.isLoading, isFalse);
+    expect(bloc.state.stats.streakDays, 10);
+  });
+
+  // ===== 7. changePeriod 相同周期 → 不改变状态（no-op）=====
+
+  test('changePeriod 相同周期时不改变状态', () async {
+    // 先完成一次正常加载
+    _stubGet(_mockResponseBody(streakDays: 3));
+    bloc.load();
+    await _waitForAsync();
+
+    final stateBefore = bloc.state;
+    expect(stateBefore.selectedPeriod, StatsPeriod.week);
+
+    // 再次调用 changePeriod(week) — 应该是 no-op
+    bloc.changePeriod(StatsPeriod.week);
+    // 不等待异步，因为不应有新请求发出
+
+    expect(bloc.state.selectedPeriod, StatsPeriod.week);
+    // state 应该完全不变（同一个对象引用）
+    expect(identical(bloc.state, stateBefore), isTrue);
+  });
+}