test(web): add component tests for 3 more untested components (GOO-54)

- ExportPdfButton (3 tests): default label, missing-target error, custom filename
- ValuationHistoryChart (3 tests): null <2 points, header/description, recharts mounting
- NotificationBell (9 tests): aria-label, badge display + 99+ cap, auth-gated
  fetchUnreadCount, dropdown toggle, empty state, item rendering, mark-all visibility

All 15 new tests pass via direct vitest. Cumulative GOO-54 progress: 29 spec
files, ~143 tests across H1-H5.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/web/components/notifications/__tests__/notification-bell.spec.tsx

@@ -0,0 +1,138 @@
+import { render, screen } from '@testing-library/react';
+import userEvent from '@testing-library/user-event';
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+
+const pushMock = vi.fn();
+vi.mock('next/navigation', () => ({
+  useRouter: () => ({ push: pushMock }),
+}));
+
+const fetchUnreadCount = vi.fn();
+const setOpen = vi.fn();
+const markAsRead = vi.fn();
+const markAllAsRead = vi.fn();
+
+let storeState: any = {
+  notifications: [],
+  unreadCount: 0,
+  isOpen: false,
+  isLoading: false,
+  setOpen,
+  markAsRead,
+  markAllAsRead,
+  fetchUnreadCount,
+};
+vi.mock('@/lib/notifications-store', () => ({
+  useNotificationsStore: () => storeState,
+}));
+
+let authState = { isAuthenticated: false };
+vi.mock('@/lib/auth-store', () => ({
+  useAuthStore: (selector: (s: typeof authState) => unknown) => selector(authState),
+}));
+
+import { NotificationBell } from '../notification-bell';
+
+beforeEach(() => {
+  pushMock.mockReset();
+  fetchUnreadCount.mockReset();
+  setOpen.mockReset();
+  markAsRead.mockReset();
+  markAllAsRead.mockReset();
+  storeState = {
+    notifications: [],
+    unreadCount: 0,
+    isOpen: false,
+    isLoading: false,
+    setOpen,
+    markAsRead,
+    markAllAsRead,
+    fetchUnreadCount,
+  };
+  authState = { isAuthenticated: false };
+});
+
+describe('NotificationBell', () => {
+  it('renders bell button with default aria-label when no unread', () => {
+    render(<NotificationBell />);
+    expect(
+      screen.getByRole('button', { name: 'Thông báo' }),
+    ).toBeInTheDocument();
+  });
+
+  it('shows unread badge with count and updates aria-label', () => {
+    storeState = { ...storeState, unreadCount: 5 };
+    render(<NotificationBell />);
+    expect(
+      screen.getByRole('button', { name: /Thông báo \(5 chưa đọc\)/ }),
+    ).toBeInTheDocument();
+    expect(screen.getByText('5')).toBeInTheDocument();
+  });
+
+  it('caps badge display at 99+ when count exceeds 99', () => {
+    storeState = { ...storeState, unreadCount: 150 };
+    render(<NotificationBell />);
+    expect(screen.getByText('99+')).toBeInTheDocument();
+  });
+
+  it('does not call fetchUnreadCount when unauthenticated', () => {
+    authState = { isAuthenticated: false };
+    render(<NotificationBell />);
+    expect(fetchUnreadCount).not.toHaveBeenCalled();
+  });
+
+  it('calls fetchUnreadCount on mount when authenticated', () => {
+    authState = { isAuthenticated: true };
+    render(<NotificationBell />);
+    expect(fetchUnreadCount).toHaveBeenCalledTimes(1);
+  });
+
+  it('toggles dropdown open via setOpen on click', async () => {
+    const user = userEvent.setup();
+    render(<NotificationBell />);
+    await user.click(screen.getByRole('button', { name: 'Thông báo' }));
+    expect(setOpen).toHaveBeenCalledWith(true);
+  });
+
+  it('renders empty state inside open dropdown', () => {
+    storeState = { ...storeState, isOpen: true };
+    render(<NotificationBell />);
+    expect(screen.getByText('Chưa có thông báo')).toBeInTheDocument();
+  });
+
+  it('renders notification items and marks unread as bold', () => {
+    storeState = {
+      ...storeState,
+      isOpen: true,
+      notifications: [
+        {
+          id: 'n1',
+          title: 'Tin mới',
+          body: 'Có người quan tâm tin của bạn',
+          isRead: false,
+          link: '/listings/1',
+          createdAt: new Date().toISOString(),
+        },
+        {
+          id: 'n2',
+          title: 'Đã đọc',
+          body: 'Cũ',
+          isRead: true,
+          link: null,
+          createdAt: new Date(Date.now() - 1000 * 60 * 60 * 25).toISOString(),
+        },
+      ],
+    };
+    render(<NotificationBell />);
+    expect(screen.getByText('Tin mới')).toBeInTheDocument();
+    expect(screen.getByText('Đã đọc')).toBeInTheDocument();
+  });
+
+  it('shows "Đánh dấu tất cả đã đọc" only when unreadCount > 0 and dropdown open', () => {
+    storeState = { ...storeState, isOpen: true, unreadCount: 3 };
+    render(<NotificationBell />);
+    expect(
+      screen.getByText('Đánh dấu tất cả đã đọc'),
+    ).toBeInTheDocument();
+  });
+});