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.
var warnUnknownProperties = function(type, props, debugID) {
  var unknownProps = [];
  for (var key in props) {
    var isValid = validateProperty(type, key, debugID);
    if (!isValid) {
      unknownProps.push(key);
    }
  }
  var unknownPropString = unknownProps.map(prop => '`' + prop + '`').join(', ');
  if (unknownProps.length === 1) {
    warning(
      false,
      'Unknown prop %s on <%s> tag. Remove this prop from the element. ' +
        'For details, see https://fb.me/react-unknown-prop%s',
      unknownPropString,
      type,
      getStackAddendum(debugID),
    );
  } else if (unknownProps.length > 1) {
    warning(
      false,
      'Unknown props %s on <%s> tag. Remove these props from the element. ' +
        'For details, see https://fb.me/react-unknown-prop%s',
      unknownPropString,
      type,
      getStackAddendum(debugID),
    );
  }
};
function validateProperties(type, props, debugID ) {