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.
const clientRenderOnBadMarkup = async (element, errorCount = 0) => {
  
  var domElement = document.createElement('div');
  domElement.innerHTML =
    '<div id="badIdWhichWillCauseMismatch" data-reactroot="" data-reactid="1"></div>';
  await renderIntoDom(element, domElement, errorCount + 1);
  
  var hydratedTextContent = domElement.textContent;
  
  const cleanDomElement = document.createElement('div');
  ExecutionEnvironment.canUseDOM = true;
  await asyncReactDOMRender(element, cleanDomElement);
  ExecutionEnvironment.canUseDOM = false;
  
  const cleanTextContent = cleanDomElement.textContent;
  
  expect(hydratedTextContent).toBe(cleanTextContent);
  
  throw new BadMarkupExpected();
};
function itRenders(desc, testFn) {