Observed this on react@16.0.0-beta.5

```js
import React from 'react';
import { renderToString } from 'react-dom/server';

const B = () => 'b';

console.log(renderToString(<div>{'a'}<B />{'c'}</div>));
```

This renders as `<div data-reactroot="">a<!-- -->bc</div>`. If you try to hydrate this you'll get the error: Text content did not match. Server: "bc" Client: "b".
}
            },
          };
        },
      };
      let e = await render(threeDivIterable);
      let parent = e.parentNode;
      expect(parent.childNodes.length).toBe(3);
      expect(parent.childNodes[0].tagName).toBe('DIV');
      expect(parent.childNodes[1].tagName).toBe('DIV');
      expect(parent.childNodes[2].tagName).toBe('DIV');
    });
    itRenders('emptyish values', async render => {
      let e = await render(0);
      expect(e.nodeType).toBe(TEXT_NODE_TYPE);
      expect(e.nodeValue).toMatch('0');
      
      
      expect((await render(<div>{''}</div>)).textContent).toBe('');
      expect(await render([])).toBe(null);
      expect(await render(false)).toBe(null);
      expect(await render(true)).toBe(null);
      expect(await render(undefined)).toBe(null);
      expect(await render([[[false]], undefined])).toBe(null);
    });
  });
  describe('property to attribute mapping', function() {
    describe('string properties', function() {
      itRenders('simple numbers', async render => {
        const e = await render(<div width={30} />);