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>{2}</div>, <div>{3}</div>));
      it('should error reconnecting different number from text', () =>
        expectMarkupMismatch(<div>{2}</div>, <div>3</div>));
      it('should error reconnecting different text in two code blocks', () =>
        expectMarkupMismatch(
          <div>{'Text1'}{'Text2'}</div>,
          <div>{'Text1'}{'Text3'}</div>,
        ));
    });
    describe('element trees and children', function() {
      it('should error reconnecting missing children', () =>
        expectMarkupMismatch(<div><div /></div>, <div />));
      it('should error reconnecting added children', () =>
        expectMarkupMismatch(<div />, <div><div /></div>));
      it('should error reconnecting more children', () =>
        expectMarkupMismatch(<div><div /></div>, <div><div /><div /></div>));
      it('should error reconnecting fewer children', () =>
        expectMarkupMismatch(<div><div /><div /></div>, <div><div /></div>));
      it('should error reconnecting reordered children', () =>
        expectMarkupMismatch(
          <div><div /><span /></div>,
          <div><span /><div /></div>,
        ));
      it('should error reconnecting a div with children separated by whitespace on the client', () =>
        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 on the server', () =>