I use `ReactDOM.unstable_renderSubtreeIntoContainer` to render a portal.

``` javascript
class Modal extends React.Component {

componentDidMount() {
    this.node = document.createElement('div');
    document.body.appendChild(this.node);
    this.renderPortal(this.props);
}

componentWillReceiveProps(nextProps) {
    this.renderPortal(nextProps);
}

componentWillUnmount() {
    ReactDOM.unmountComponentAtNode(this.node);
    document.body.removeChild(this.node);
}

renderPortal = (props) => {
    renderSubtreeIntoContainer(this, <ModalPortal {...props} />, this.node);
}

render() {
    return null;
  }
}
```

In my root component:

``` javascript
class App extends React.Component {
    static childContextTypes = {
        highlightColor: React.PropTypes.object
    }

    getChildContext() {
        return {
            highlightColor: this.props.highlightColor
        }
    }

    ...
}
```

The context of root component will be updated and passed to children if  `this.props.highlightColor` is changed. This is right.
I can access the correct context in the `<ModalPortal/>` component in the first render.
And after that the context passed to  `<ModalPortal/>` **does not change any more** when the context of root component changed.
But I can access the correct context in the `<Modal/>`  every render.

what's wrong with my code ?

var Component = React.createClass({
      contextTypes: {
        foo: React.PropTypes.string.isRequired,
      },
      render: function() {
        return <div>{this.context.foo}</div>;
      },
    });
    var Parent = React.createClass({
      childContextTypes: {
        foo: React.PropTypes.string.isRequired,
      },
      getChildContext: function() {
        return {
          foo: 'bar',
        };
      },
      render: function() {
        return null;
      },
      componentDidMount: function() {
        expect(function() {
          renderSubtreeIntoContainer(this, <Component />, portal);
        }.bind(this)).not.toThrow();
      },
    });
    ReactTestUtils.renderIntoDocument(<Parent />);
    expect(portal.firstChild.innerHTML).toBe('bar');
  });
  it('should throw if parentComponent is invalid', function() {