attempting to trigger the issue @sebmarkbage described

facebook#8751 (comment)

Author: iamdustan

src/renderers/shared/shared/__tests__/refs-test.js

@@ -230,7 +230,6 @@ describe('ref swapping', () => {
     expect(refHopsAround.refs.divThreeRef).toEqual(thirdDiv);
   });
 
-
   it('always has a value for this.refs', () => {
     class Component extends React.Component {
       render() {
@@ -392,3 +391,42 @@ describe('string refs between fiber and stack', () => {
     }
   });
 });
+
+describe('root level refs', () => {
+  it('attaches and detaches root refs in stack', () => {
+    assertForRenderer(require('ReactDOM'));
+  });
+
+  it('attaches and detaches root refs in fiber', () => {
+    assertForRenderer(require('ReactDOMFiber'));
+  });
+
+  const assertForRenderer = (DOM) => {
+    spyOn(console, 'error');
+    var ref = jest.fn();
+    var container = document.createElement('div');
+    var result = DOM.render(<div ref={ref} />, container);
+    expect(ref).toHaveBeenCalledTimes(1);
+    expect(ref.mock.calls[0][0]).toBeInstanceOf(HTMLDivElement);
+    expect(result).toBe(ref.mock.calls[0][0]);
+    DOM.unmountComponentAtNode(container);
+    expect(ref).toHaveBeenCalledTimes(2);
+    expect(ref.mock.calls[1][0]).toBe(null);
+
+    class Comp extends React.Component {
+      render() {
+        return <div>Comp</div>;
+      }
+    }
+
+    ref = jest.fn();
+    result = DOM.render(<Comp ref={ref}/>, container);
+
+    expect(ref).toHaveBeenCalledTimes(1);
+    expect(ref.mock.calls[0][0]).toBeInstanceOf(Comp);
+    expect(result).toBe(ref.mock.calls[0][0]);
+    DOM.unmountComponentAtNode(container);
+    expect(ref).toHaveBeenCalledTimes(2);
+    expect(ref.mock.calls[1][0]).toBe(null);
+  };
+});