Currently if React is not loaded, ReactDOM shows this:

<img width="664" alt="screen shot 2017-08-08 at 3 36 52 pm" src="https://user-images.githubusercontent.com/810438/29077217-784c7624-7c4f-11e7-88bc-b055407523a9.png">

We should throw a nicer error message in the entry point I think.
container,
      );
      
      
      expect(ops).toEqual(['B']);
      ops = [];
      
      click(node);
      expect(ops).toEqual(['A']);
    });
    it('should not crash encountering low-priority tree', () => {
      ReactDOM.render(
        <div hidden={true}>
          <div />
        </div>,
        container,
      );
    });
    it('should not warn when rendering into an empty container', () => {
      spyOn(console, 'error');
      ReactDOM.render(<div>foo</div>, container);
      expect(container.innerHTML).toBe('<div>foo</div>');
      ReactDOM.render(null, container);
      expect(container.innerHTML).toBe('');
      expectDev(console.error.calls.count()).toBe(0);
      ReactDOM.render(<div>bar</div>, container);
      expect(container.innerHTML).toBe('<div>bar</div>');
      expectDev(console.error.calls.count()).toBe(0);
    });
    it('should warn when replacing a container which was manually updated outside of React', () => {