✅(frontend) add unit test for mobile rendering in docheaderinfo

ensures numchild count is displayed correctly on mobile interface

Signed-off-by: Cyril <c.gromoff@gmail.com>

Author: Ovgodd

src/frontend/apps/impress/src/features/docs/doc-header/__tests__/DocHeaderInfo.spec.tsx

@@ -0,0 +1,46 @@
+import { render, screen } from '@testing-library/react';
+import React from 'react';
+import { describe, expect, test, vi } from 'vitest';
+
+import { AppWrapper } from '@/tests/utils';
+
+// Force mobile layout so the children count is rendered
+vi.mock('@/stores', () => ({
+  useResponsiveStore: () => ({ isDesktop: false }),
+}));
+
+// Provide stable mocks for hooks used by the component
+vi.mock('../../doc-management', async () => {
+  const actual = await vi.importActual<any>('../../doc-management');
+  return {
+    ...actual,
+    useTrans: () => ({ transRole: vi.fn((r) => String(r)) }),
+    useIsCollaborativeEditable: () => ({ isEditable: true }),
+  };
+});
+
+vi.mock('@/core', () => ({
+  useConfig: () => ({ data: {} }),
+}));
+
+vi.mock('@/hook', () => ({
+  useDate: () => ({
+    relativeDate: () => 'yesterday',
+    calculateDaysLeft: () => 5,
+  }),
+}));
+
+import { DocHeaderInfo } from '../components/DocHeaderInfo';
+
+describe('DocHeaderInfo', () => {
+  test('renders the number of sub-documents when numchild is provided (mobile layout)', () => {
+    const doc = {
+      numchild: 3,
+      updated_at: new Date().toISOString(),
+    } as any;
+
+    render(<DocHeaderInfo doc={doc} />, { wrapper: AppWrapper });
+
+    expect(screen.getByText(/Contains 3 sub-documents/i)).toBeInTheDocument();
+  });
+});