테마 영속화 테스트 추가

userfront/test/theme_controller_test.dart

@@ -0,0 +1,32 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+import 'package:userfront/core/theme/theme_controller.dart';
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  setUp(() async {
+    SharedPreferences.setMockInitialValues({});
+    await ThemeController.instance.setThemeMode(ThemeMode.light);
+  });
+
+  test('저장된 dark 값을 복원한다', () async {
+    SharedPreferences.setMockInitialValues({
+      ThemeController.storageKey: 'dark',
+    });
+
+    await ThemeController.instance.restore();
+
+    expect(ThemeController.instance.value, ThemeMode.dark);
+  });
+
+  test('toggle 결과를 저장한다', () async {
+    await ThemeController.instance.restore();
+    await ThemeController.instance.toggle();
+
+    final prefs = await SharedPreferences.getInstance();
+    expect(ThemeController.instance.value, ThemeMode.dark);
+    expect(prefs.getString(ThemeController.storageKey), 'dark');
+  });
+}