add test

packages/react-dom/src/__tests__/ReactDOMFiber-test.js

@@ -19,12 +19,23 @@ let act;
 let assertConsoleErrorDev;
 let assertLog;
 let root;
+let JSDOM
 
 describe('ReactDOMFiber', () => {
   let container;
 
   beforeEach(() => {
     jest.resetModules();
+
+    // JSDOM needs to be setup with a TextEncoder and TextDecoder when used standalone
+    // https://github.com/jsdom/jsdom/issues/2524
+    (() => {
+      const { TextEncoder, TextDecoder } = require('util');
+      global.TextEncoder = TextEncoder;
+      global.TextDecoder = TextDecoder;
+      JSDOM = require('jsdom').JSDOM;
+    })();
+
     React = require('react');
     ReactDOM = require('react-dom');
     PropTypes = require('prop-types');
@@ -1272,4 +1283,48 @@ describe('ReactDOMFiber', () => {
     });
     expect(didCallOnChange).toBe(true);
   });
+
+  it('should restore selection in the correct window', async () => {
+    // creating new JSOM instance to get a second window as window.open is not implemented
+    // https://github.com/jsdom/jsdom/blob/c53efc81e75f38a0558fbf3ed75d30b78b4c4898/lib/jsdom/browser/Window.js#L987
+    const {window: newWindow} = new JSDOM('');
+    // creating a new container since the default cleanup expects the existing container to be in the document
+    const newContainer = newWindow.document.createElement('div');
+    newWindow.document.body.appendChild(newContainer);
+    root = ReactDOMClient.createRoot(newContainer);
+
+    const Test = () => {
+      const [reverse, setReverse] = React.useState(false);
+      const [items] = React.useState(() => ['a', 'b', 'c']);
+      const onClick = () => {
+        setReverse(true);
+      };
+
+      // shuffle the items so that the react commit needs to restore focus
+      // to the correct element after commit
+      const itemsToRender = reverse ? items.reverse() : items;
+
+      return (
+        <div>
+          {itemsToRender.map(item => (
+            <button onClick={onClick} key={item} id={item}>
+              {item}
+            </button>
+          ))}
+        </div>
+      );
+    };
+
+    await act(() => {
+      root.render(<Test />);
+    });
+
+    newWindow.document.getElementById('a').focus();
+    await act(() => {
+      newWindow.document.getElementById('a').click();
+    });
+
+    expect(newWindow.document.activeElement).not.toBe(newWindow.document.body);
+    expect(newWindow.document.activeElement.innerHTML).toBe('a');
+  });
 });