See the issue and the test case with original fix in https://github.com/facebook/react/pull/14802.

We'll need to fix it properly, see https://github.com/facebook/react/pull/14802#issuecomment-463277621.
return props.foo === nextProps.foo;
    }
    const Foo = React.memo(({foo, bar}) => {
      renderCount++;
      return (
        <div>
          {foo} {bar}
        </div>
      );
    }, areEqual);
    const shallowRenderer = createRenderer();