test: simplify test case (#38403)

components/grid/__tests__/cached-row-context.test.tsx

@@ -1,48 +1,38 @@
-import React, { memo, useContext, useRef, useState } from 'react';
+import React, { memo, useContext } from 'react';
 import Row from '../row';
 import RowContext from '../RowContext';
-import { render, fireEvent } from '../../../tests/utils';
+import { fireEvent, pureRender } from '../../../tests/utils';
 
-const CacheInner = memo(() => {
-  const countRef = useRef(0);
-  countRef.current++;
-  useContext(RowContext);
-  return (
-    <div>
-      Child Rendering Count: <span id="child_count">{countRef.current}</span>
-    </div>
-  );
-});
+let innerCount = 0;
+let outerCount = 0;
 
-const CacheOuter = () => {
-  const [count, setCount] = useState(1);
-  const handleClick = () => {
-    setCount(count + 1);
-  };
-  return (
-    <div>
-      <button type="button" onClick={handleClick} id="parent_btn">
-        Click
-      </button>
-      Parent Rendering Count: <span id="parent_count">{count}</span>
-      <Row>
-        <CacheInner />
-      </Row>
-    </div>
-  );
+const handleClick = () => {
+  outerCount++;
 };
 
-it('Cached RowContext is working', () => {
-  const { container } = render(<CacheOuter />);
-  const childCount = container.querySelector('#child_count')?.textContent;
+const CacheInner: React.FC = memo(() => {
+  innerCount++;
+  useContext(RowContext);
+  return null;
+});
 
-  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 CacheOuter: React.FC = memo(() => (
+  <>
+    <button type="button" onClick={handleClick} id="parent_btn">
+      Click
+    </button>
+    <Row>
+      <CacheInner />
+    </Row>
+  </>
+));
 
+it('Cached RowContext is working', () => {
+  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);
+  expect(outerCount).toBe(1);
+  expect(innerCount).toBe(1);
+  unmount();
 });