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 domElement = await serverRender(serverElement);
  resetModules();
  return renderIntoDom(
    clientElement,
    domElement.parentNode,
    shouldMatch ? 0 : 1,
  );
}
function expectMarkupMatch(serverElement, clientElement) {
  return testMarkupMatch(serverElement, clientElement, true);
}
function expectMarkupMismatch(serverElement, clientElement) {
  return testMarkupMatch(serverElement, clientElement, false);
}
let onAfterResetModules = null;
function resetModules() {
  jest.resetModuleRegistry();
  PropTypes = require('prop-types');
  React = require('react');
  ReactDOM = require('react-dom');
  ReactDOMServer = require('react-dom/server');
  ReactDOMFeatureFlags = require('ReactDOMFeatureFlags');