Run the [`fixtures/ssr` test harness](https://github.com/facebook/react/tree/master/fixtures/ssr). In the terminal, the following warning is logged:

```
Warning: Unknown prop `onClick` on <a> tag. Remove this prop from the element. For details, see https://fb.me/react-unknown-prop
  in a (at Page.js:12)
  in p (at Page.js:18)
  in div (at Page.js:17)
  in Page (at App.js:12)
  in div (at App.js:10)
  in body (at Chrome.js:17)
  in html (at Chrome.js:9)
  in Chrome (at App.js:9)
  in App (at render.js:18)
```

SSR behavior should match client-side behavior and not warn for a valid attribute.
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', () =>
        (ReactDOMFeatureFlags.useFiber
          ? expectMarkupMatch
          : expectMarkupMismatch)(
          <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'/>"}} />,
      ));