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.childNodes.length).toBe(0);
            expect(e.textContent).toBe('');
          } else {
            expect(e.childNodes.length).toBe(3);
            expectTextNode(e.childNodes[0], '');
            expectTextNode(e.childNodes[1], '');
            expectTextNode(e.childNodes[2], '');
          }
        } else {
          
          expect(e.childNodes.length).toBe(6);
          expectTextNode(e.childNodes[0], '');
          expectTextNode(e.childNodes[2], '');
          expectTextNode(e.childNodes[4], '');
        }
      });
      itRenders('a div with multiple whitespace children', async render => {
        const e = await render(<div>{' '}{' '}{' '}</div>);
        if (ReactDOMFeatureFlags.useFiber) {
          
          if (
            render === serverRender ||
            render === clientRenderOnServerString ||
            render === streamRender
          ) {
            
            
            expect(e.childNodes.length).toBe(5);
            expectTextNode(e.childNodes[0], ' ');
            expectTextNode(e.childNodes[2], ' ');