test: simplify test case (#38375)

components/menu/__tests__/cached-context.test.tsx

@@ -1,55 +1,42 @@
-import React, { memo, useContext, useRef, useState } from 'react';
+import React, { memo, useContext } from 'react';
 import Menu from '../index';
 import MenuContext from '../MenuContext';
-import { render, fireEvent } from '../../../tests/utils';
+import { fireEvent, pureRender } from '../../../tests/utils';
+
+let innerCount = 0;
+let outerCount = 0;
+
+const handleClick = () => {
+  outerCount++;
+};
 
 // we use'memo' here in order to only render inner component while context changed.
-const CacheInner = memo(() => {
-  const countRef = useRef(0);
-  countRef.current++;
-  // subscribe anchor context
+const CacheInner: React.FC = memo(() => {
+  innerCount++;
+  // subscribe locale context
   useContext(MenuContext);
-  return (
-    <div>
-      Child Rendering Count: <span id="child_count">{countRef.current}</span>
-    </div>
-  );
+  return null;
 });
 
-const CacheOuter = () => {
-  // We use 'useState' here in order to trigger parent component rendering.
-  const [count, setCount] = useState(1);
-  const handleClick = () => {
-    setCount(count + 1);
-  };
-  // During each rendering phase, the cached context value returned from method 'Menu#getMemoizedContextValue' will take effect.
-  // So 'CacheInner' component won't rerender.
-  return (
-    <div>
+const CacheOuter: React.FC = memo(() => (
+  <>
     <button type="button" onClick={handleClick} id="parent_btn">
       Click
     </button>
-      Parent Rendering Count: <span id="parent_count">{count}</span>
     <Menu>
       <Menu.Item key="test">
         <CacheInner />
       </Menu.Item>
     </Menu>
-    </div>
-  );
-};
+  </>
+));
 
 it("Rendering on Menu without changed MenuContext won't trigger rendering on child component.", () => {
-  const { container, unmount } = render(<CacheOuter />);
-  const childCount = container.querySelector('#child_count')?.textContent;
-  fireEvent.click(container.querySelector('#parent_btn')!);
-  expect(container.querySelector('#parent_count')?.textContent).toBe('2');
-  // child component won't rerender
-  expect(container.querySelector('#child_count')?.textContent).toBe(childCount);
+  const { container, unmount } = pureRender(<CacheOuter />);
+  expect(outerCount).toBe(0);
+  expect(innerCount).toBe(1);
   fireEvent.click(container.querySelector('#parent_btn')!);
-  expect(container.querySelector('#parent_count')?.textContent).toBe('3');
-  // child component won't rerender
-  expect(container.querySelector('#child_count')?.textContent).toBe(childCount);
-  // in order to depress warning "Warning: An update to Menu inside a test was not wrapped in act(...)."
+  expect(outerCount).toBe(1);
+  expect(innerCount).toBe(1);
   unmount();
 });