test(HeaderSideNavItems): add tests (#13303)

Co-authored-by: kodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>

packages/react/src/components/UIShell/__tests__/HeaderSideNavItems-test.js

@@ -0,0 +1,40 @@
+/**
+ * Copyright IBM Corp. 2022
+ *
+ * This source code is licensed under the Apache-2.0 license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import React from 'react';
+import HeaderSideNavItems from '../HeaderSideNavItems';
+import { render, screen } from '@testing-library/react';
+import HeaderMenuItem from '../HeaderMenuItem';
+
+describe('HeaderSideNavItems', () => {
+  describe('renders as expected - Component API', () => {
+    it('should render children as expected', () => {
+      render(
+        <HeaderSideNavItems>
+          <HeaderMenuItem href="#">Link 1</HeaderMenuItem>
+          <HeaderMenuItem href="#">Link 2</HeaderMenuItem>
+        </HeaderSideNavItems>
+      );
+
+      expect(screen.getAllByRole('listitem')).toHaveLength(2);
+    });
+
+    it('should support a custom `className` prop on the outermost element', () => {
+      const { container } = render(
+        <HeaderSideNavItems className="custom-class" />
+      );
+
+      expect(container.firstChild).toHaveClass('custom-class');
+    });
+
+    it('should respect hasDivider prop', () => {
+      const { container } = render(<HeaderSideNavItems hasDivider />);
+
+      expect(container.firstChild).toHaveClass('cds--side-nav__header-divider');
+    });
+  });
+});