test(react-button): add SplitButton regression test before base-hook extraction

change/@fluentui-react-button-9244ff4e-e1f6-48df-a3fb-1d459975c232.json

@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "test: add SplitButton regression coverage for ref forwarding, default menu icon, and slot element metadata",
+  "packageName": "@fluentui/react-button",
+  "email": "vgenaev@gmail.com",
+  "dependentChangeType": "patch"
+}

packages/react-components/react-button/library/src/components/SplitButton/SplitButton.test.tsx

@@ -1,8 +1,13 @@
 import * as React from 'react';
 import { render } from '@testing-library/react';
+import { renderHook } from '@testing-library/react-hooks';
 import userEvent from '@testing-library/user-event';
+import { isSlot, SLOT_ELEMENT_TYPE_SYMBOL } from '@fluentui/react-utilities';
 import { isConformant } from '../../testing/isConformant';
 import { SplitButton } from './SplitButton';
+import { Button } from '../Button/Button';
+import { MenuButton } from '../MenuButton/MenuButton';
+import { useSplitButton_unstable } from './useSplitButton';
 import type { SplitButtonProps } from './SplitButton.types';
 
 describe('SplitButton', () => {
@@ -176,4 +181,51 @@ describe('SplitButton', () => {
     userEvent.click(primaryActionButton);
     expect(onClick).not.toHaveBeenCalled();
   });
+
+  it('forwards a ref to the root DIV element', () => {
+    let rootElement: Element | null = null;
+    const { container } = render(
+      <SplitButton
+        ref={node => {
+          rootElement = node;
+        }}
+      >
+        This is a button
+      </SplitButton>,
+    );
+
+    expect(rootElement).toBeInstanceOf(HTMLDivElement);
+    expect(rootElement).toBe(container.firstElementChild);
+  });
+
+  it('renders the default styled menu icon (chevron) when no menu icon is provided', () => {
+    const { getAllByRole } = render(<SplitButton>This is a button</SplitButton>);
+    const [, menuButton] = getAllByRole('button');
+
+    expect(menuButton.querySelector('svg')).toBeTruthy();
+  });
+
+  it('renders an explicit menu icon instead of the default chevron', () => {
+    const { getAllByRole } = render(<SplitButton menuIcon="Test MenuIcon">This is a button</SplitButton>);
+    const [, menuButton] = getAllByRole('button');
+
+    expect(menuButton.textContent).toBe('Test MenuIcon');
+    expect(menuButton.querySelector('svg')).toBeFalsy();
+  });
+
+  it('resolves child slot element metadata to the styled Button and MenuButton components', () => {
+    const { result } = renderHook(() => useSplitButton_unstable({ children: 'This is a button' }, React.createRef()));
+
+    const { primaryActionButton, menuButton } = result.current;
+
+    expect(isSlot(primaryActionButton)).toBe(true);
+    expect(isSlot(menuButton)).toBe(true);
+
+    if (!isSlot(primaryActionButton) || !isSlot(menuButton)) {
+      return;
+    }
+
+    expect(primaryActionButton[SLOT_ELEMENT_TYPE_SYMBOL]).toBe(Button);
+    expect(menuButton[SLOT_ELEMENT_TYPE_SYMBOL]).toBe(MenuButton);
+  });
 });