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.
return expectErrors(async () => {
    ExecutionEnvironment.canUseDOM = true;
    await asyncReactDOMRender(reactElement, domElement);
    ExecutionEnvironment.canUseDOM = false;
    return domElement.firstChild;
  }, errorCount);
}
async function renderIntoString(reactElement, errorCount = 0) {
  return await expectErrors(
    () =>
      new Promise(resolve =>
        resolve(ReactDOMServer.renderToString(reactElement)),
      ),
    errorCount,
  );
}
async function serverRender(reactElement, errorCount = 0) {
  const markup = await renderIntoString(reactElement, errorCount);
  var domElement = document.createElement('div');
  domElement.innerHTML = markup;
  return domElement.firstChild;
}
class DrainWritable extends stream.Writable {