feat: 增加测试覆盖率并优化代码质量

test: 添加单元测试和端到端测试
refactor: 重构登录页面和上传模块
ci: 更新测试覆盖率阈值至42%
build: 添加测试相关依赖
docs: 更新测试文档
style: 修复代码格式问题

src/components/layout/breadcrumb.test.tsx

@@ -0,0 +1,52 @@
+import { render, screen } from '@testing-library/react';
+import '@testing-library/jest-dom';
+import { Breadcrumb } from './breadcrumb';
+
+jest.mock('next/link', () => {
+  return ({ children, href }: { children: React.ReactNode; href: string }) => {
+    return <a href={href}>{children}</a>;
+  };
+});
+
+describe('Breadcrumb', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  describe('Rendering', () => {
+    it('should render breadcrumb component', () => {
+      render(<Breadcrumb items={[]} />);
+      const nav = screen.getByRole('navigation', { name: /breadcrumb/i });
+      expect(nav).toBeInTheDocument();
+    });
+
+    it('should render home link', () => {
+      render(<Breadcrumb items={[]} />);
+      const homeLinks = screen.getAllByRole('link');
+      expect(homeLinks.length).toBeGreaterThan(0);
+    });
+
+    it('should render breadcrumb items', () => {
+      const items = [
+        { label: 'Products', href: '/products' },
+        { label: 'Details', href: '/products/1' },
+      ];
+      
+      render(<Breadcrumb items={items} />);
+      
+      const productLink = screen.getByRole('link', { name: /Products/i });
+      const detailsLink = screen.getByRole('link', { name: /Details/i });
+      
+      expect(productLink).toBeInTheDocument();
+      expect(detailsLink).toBeInTheDocument();
+    });
+  });
+
+  describe('Accessibility', () => {
+    it('should have nav element with aria-label', () => {
+      render(<Breadcrumb items={[]} />);
+      const nav = screen.getByRole('navigation', { name: /breadcrumb/i });
+      expect(nav).toBeInTheDocument();
+    });
+  });
+});