It seems problematic to allow arbitary non-lowercase attribute on HTML nodes. Because the server has no ability to keep them case sensitive (HTML isn't). So they will end up different on the client.

We should probably warn if the attribute is not a known one *and* is not lowercase.
return <div>{context.text}</div>;
      }
      Grandchild.contextTypes = {text: PropTypes.string};
      const Child = props => <Grandchild />;
      const e = await render(<PurpleContext><Child /></PurpleContext>);
      expect(e.textContent).toBe('purple');
    });
    itRenders('a child context overriding a parent context', async render => {
      const Grandchild = (props, context) => {
        return <div>{context.text}</div>;
      };
      Grandchild.contextTypes = {text: PropTypes.string};
      const e = await render(
        <PurpleContext><RedContext><Grandchild /></RedContext></PurpleContext>,
      );
      expect(e.textContent).toBe('red');
    });
    itRenders('a child context merged with a parent context', async render => {
      class Parent extends React.Component {
        getChildContext() {
          return {text1: 'purple'};
        }
        render() {
          return <Child />;
        }
      }
      Parent.childContextTypes = {text1: PropTypes.string};
      class Child extends React.Component {