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".
));
      it('should error reconnecting a div with children separated by different whitespace on the server', () =>
        expectMarkupMismatch(
          
          <div id="parent"><div id="child1" />      <div id="child2" /></div>, 
          <div id="parent"><div id="child1" /><div id="child2" /></div>,
        ));
      it('should error reconnecting a div with children separated by different whitespace', () =>
        expectMarkupMismatch(
          <div id="parent"><div id="child1" /> <div id="child2" /></div>,
          
          <div id="parent"><div id="child1" />      <div id="child2" /></div>, 
        ));
      it('can distinguish an empty component from a dom node', () =>
        expectMarkupMismatch(
          <div><span /></div>,
          <div><EmptyComponent /></div>,
        ));
      it('can distinguish an empty component from an empty text component', () =>
        expectMarkupMatch(<div><EmptyComponent /></div>, <div>{''}</div>));
    });
    
    it('should error reconnecting a div with different dangerouslySetInnerHTML', () =>
      expectMarkupMismatch(
        <div dangerouslySetInnerHTML={{__html: "<span id='child1'/>"}} />,
        <div dangerouslySetInnerHTML={{__html: "<span id='child2'/>"}} />,
      ));
  });
});