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.
expect(e.hasAttribute('foo')).toBe(false);
        },
      );
      itRenders(
        'unknown attributes for custom elements using is',
        async render => {
          const e = await render(<div is="custom-element" foo="bar" />);
          expect(e.getAttribute('foo')).toBe('bar');
        },
      );
      itRenders(
        'no unknown attributes for custom elements using is with null value',
        async render => {
          const e = await render(<div is="custom-element" foo={null} />);
          expect(e.hasAttribute('foo')).toBe(false);
        },
      );
    });
    itRenders('no HTML events', async render => {
      const e = await render(<div onClick={() => {}} />);
      expect(e.getAttribute('onClick')).toBe(null);
      expect(e.getAttribute('onClick')).toBe(null);
      expect(e.getAttribute('click')).toBe(null);
    });
  });
  describe('elements and children', function() {
    
    const TEXT_NODE_TYPE = 3;
    const COMMENT_NODE_TYPE = 8;
    function expectNode(node, type, value) {