There was a test added as part of shallow renderer rewrite (#9426) in https://github.com/facebook/react/pull/9426/commits/fc1c6f913cb74a2cb1ce1cfe6ba91b431786c4ac that I don’t understand.

It tests that you can take an *instance*, call `cloneElement` on it, and pass the result to the shallow renderer. If we are doing this internally this seems like a misunderstanding of how the API should work, and we need to fix those callsites to read `getRenderOutput()` instead of `getMountedInstance()`.

You can see the test is wrong because if you change it to render to a *different* shallow renderer like this

```js
    const shallowRenderer = createRenderer();
    let result = shallowRenderer.render(<SimpleComponent foo="foo" />);
    expect(result).toEqual(<div>foo:bar</div>);
    const instance = shallowRenderer.getMountedInstance();

    const shallowRenderer2 = createRenderer();
    const cloned = React.cloneElement(instance, {foo: 'baz'});
    result = shallowRenderer2.render(cloned);
    expect(result).toEqual(<div>baz:bar</div>);
```

it will fail with 

```
TypeError: Cannot read property 'prototype' of undefined
```

The argument we’re passing in this case is **not** a proper React element and doesn’t actually have `element.type`. It just mostly “happens” to work because both React elements and ShallowRenderer instances have `.props` on them, and code almost doesn’t read anything else in the update path. This [is an example hack](https://github.com/facebook/react/blob/779d23f72e7f2c763f7a3e3373a4134c54356fd6/packages/react-test-renderer/src/ReactShallowRenderer.js#L147-L148) that we needed because of this.

I think we should just delete this test, and fix the internal callsites. It was never intentionally supported, and prevents me from doing some other fixes in the shalllow renderer.
state = {update: false};
      shouldComponentUpdate(nextProps, nextState) {
        return this.state.update !== nextState.update;
      }
      render() {
        renderCounter++;
        return <div>{`${renderCounter}`}</div>;
      }
    }
    const shallowRenderer = createRenderer();
    shallowRenderer.render(<SimpleComponent />);
    expect(shallowRenderer.getRenderOutput()).toEqual(<div>1</div>);
    const instance = shallowRenderer.getMountedInstance();
    instance.setState({update: false});
    expect(shallowRenderer.getRenderOutput()).toEqual(<div>1</div>);
    instance.setState({update: true});
    expect(shallowRenderer.getRenderOutput()).toEqual(<div>2</div>);
  });
  it('should enable PureComponent to prevent a re-render', () => {
    let renderCounter = 0;
    class SimpleComponent extends React.PureComponent {